door results animals becoming interested handle trial error learn operate handle open door local enhancement demonstrator attracts observer 's attention particular location ref name mechanisms ref local enhancement observed transmit foraging information among birds rats pigs ref name foraging ref stingless bee ''trigona corvina'' uses local enhancement locate members colony food resources social transmission well documented example social transmission behaviour occurred group macaques hachijojima island japan macaques lived inland forest


learning teacher demonstrator adjusts behaviour increase probability pupil observer achieving desired end result behaviour example killer whales known intentionally beach catch pinniped prey ref name rendell ref mother killer whales teach young catch pinnipeds pushing onto shore encouraging attack prey mother killer whale altering behaviour help offspring learn catch prey evidence teaching ref name rendell teaching limited mammals many insects example observed demonstrating various forms

Natural science
Biology
Zoology
Ethology


teaching obtain food ants example guide food sources process called tandem running ant guide companion ant source food ref name hoppit ref suggested pupil ant able learn route obtain food future teach route ants behaviour teaching also exemplified crows specifically new caledonian crows adults whether individual families teach young adolescent offspring construct utilize tools example ''pandanus'' branches used


extract insects larvae holes within trees mating fight supremacy individual reproduction important phase proliferation individuals genes within species reason exist complex mating rituals complex even often regarded fixed action patterns stickleback 's complex mating ritual studied tinbergen regarded notable example often social life animals fight right reproduce well social supremacy common example fighting social sexual supremacy called pecking


establishes scratch living groups several animal species including humans tend live groups group size major aspect social environment social life probably complex effective survival strategy may regarded sort symbiosis among individuals species society composed group individuals belonging species living within well defined rules food management role assignments reciprocal dependence biologists interested evolution theory first started examining social behaviour apparently unanswerable questions arose birth sterile


castes like bees could explained evolving mechanism emphasizes reproductive success many individuals possible amongst animals living small groups like squirrels individual would risk life save rest group behaviours may examples altruism course behaviours altruistic indicated table example revengeful behaviour one point claimed observed exclusively ''homo sapiens'' however species reported vengeful including chimpanzees ref name mccullough ref well anecdotal reports


vengeful camels ref name waal ref class wikitable text align center classification social behaviours type behaviour effect donor effect receiver egoistic neutral increases fitness decreases fitness cooperative neutral increases fitness neutral increases fitness altruistic decreases fitness neutral increases fitness revengeful decreases fitness decreases fitness altruistic behaviour explained gene centred view evolution benefits costs group living one advantage group living decreased predation


number predator attacks stays despite increasing prey group size prey may reduced risk predator attacks dilution effect ref name davies ref according selfish herd theory fitness benefits associated group living vary depending location individual within group theory suggests conspecifics positioned centre group reduce likelihood predations periphery become vulnerable attack additionally predator confused mass individuals find difficult single one


target reason zebra 's stripes offer camouflage habitat tall grasses also advantage blending herd zebras groups prey also actively reduce predation risk effective defence tactics earlier detection predators increased vigilance ref name davies another advantage group living increased ability forage food group members may exchange information food sources one another facilitating process resource location ref name davies honeybees notable example using waggle dance communicate


location flowers rest hive predators also receive benefits hunting groups using better strategies able take larger prey ref name davies disadvantages accompany living groups living close proximity animals facilitate transmission parasites disease groups large may also experience greater competition resources mates group size theoretically social animals optimal group sizes maximize benefits minimize costs group living however nature groups stable slightly larger optimal sizes ref


name davies generally benefits individual join optimally sized group despite slightly decreasing advantage members groups may continue increase size advantageous remain alone join overly full group tinbergen 's four questions ethologists niko tinbergen argued ethology always needed include four kinds explanation instance behaviour function behaviour affect animal 's chances survival reproduction animal respond way instead way causation stimuli elicit


response modified recent learning development behaviour change age early experiences necessary animal display behaviour evolutionary history behaviour compare similar behaviour related species might begun process phylogeny explanations complementary rather mutually exclusive instances behaviour require explanation four levels example function eating acquire nutrients ultimately aids survival reproduction immediate cause eating


hunger causation hunger eating evolutionarily ancient found many species evolutionary history develop early within organism 's lifespan development easy confuse questions example argue people eat 're hungry acquire nutrients without realizing reason people experience hunger causes acquire nutrients see also anthrozoology behavioral ecology cognitive ethology deception animals human ethology list abnormal behaviours animals references reading http dmrbsuedu utils getfile collection conspectush id filename pdf burkhardt richard w jr emergence ethology scientific discipline conspectus history


ethology articles containing video clips


'''electrical engineering''' engineering discipline concerned study design application equipment devices systems use electricity electronics electromagnetism emerged identifiable occupation latter half th century commercialization electric telegraph telephone electrical power generation distribution use electrical engineering divided wide range different fields including computer engineering systems engineering power engineering telecommunications radio frequency engineering signal processing instrumentation photovoltaic cells electronics optics photonics many disciplines overlap engineering branches spanning huge number

Applied science
Engineering and technology
Electrical Engineering


specializations including hardware engineering power electronics electromagnetics waves microwave engineering nanotechnology electrochemistry renewable energies mechatronics control electrical materials science electrical engineers typically hold degree electrical engineering electronic engineering practising engineers may professional certification members professional body international standards organization include international electrotechnical commission iec institute electrical electronics engineers ieee institution engineering technology iet '' formerly iee '' electrical engineers work wide range industries skills required likewise variable range circuit theory


management skills project manager tools equipment individual engineer may need similarly variable ranging simple voltmeter sophisticated design manufacturing software history electricity subject scientific interest since least early th century william gilbert prominent early electrical scientist first draw clear distinction magnetism static electricity credited establishing term electricity also designed versorium device detects presence statically charged objects swedish professor johan wilcke invented device


later named electrophorus produced static electric charge alessandro volta developed voltaic pile forerunner electric battery th century discoveries michael faraday formed foundation electric motor technology th century research subject started intensify notable developments century include work hans christian rsted discovered electric current produces magnetic field deflect compass needle william sturgeon invented electromagnet joseph henry edward davy invented electrical relay


georg ohm quantified relationship electric current potential difference conductor michael faraday discoverer electromagnetic induction james clerk maxwell published unified theory electricity magnetism treatise ''electricity magnetism'' georges louis le sage developed presented berlin probably world 's first form electric telegraphy using different wires one letter alphabet telegraph connected two rooms electrostatic telegraph moved gold leaf electrical conduction


francisco salva campillo proposed electrostatic telegraph system worked electrical telegraphy presented report royal academy natural sciences arts barcelona salva 's electrolyte telegraph system innovative though greatly influenced based upon two new discoveries made europe alessandro volta 's electric battery generating electric current william nicholson anthony carlyle 's electrolysis water electrical telegraphy may considered first example electrical engineering electrical engineering became profession later th century


practitioners created global electric telegraph network first professional electrical engineering institutions founded uk usa support new discipline francis ronalds created electric telegraph system documented vision world could transformed electricity years later joined new society telegraph engineers soon renamed institution electrical engineers regarded members first cohort end th century world forever changed rapid communication


made possible engineering development land lines submarine cables wireless telegraphy practical applications advances fields created increasing need standardised units measure led international standardization units volt ampere coulomb ohm farad henry achieved international conference chicago publication standards formed basis future advances standardisation various industries many countries definitions immediately recognized relevant legislation years study electricity largely considered


subfield physics since early electrical technology considered electromechanical nature technische universit darmstadt founded world 's first department electrical engineering introduced first degree course electrical engineering first electrical engineering degree program united states started massachusetts institute technology mit physics department professor charles cross though cornell university produce world 's first electrical engineering graduates first course electrical engineering taught cornell 's sibley college mechanical engineering mechanic arts


cornell president andrew dickson white established first department electrical engineering united states year university college london founded first chair electrical engineering great britain professor mendell p weinbach university missouri soon followed suit establishing electrical engineering department afterwards universities institutes technology gradually started offer electrical engineering programs students world decades use electrical engineering increased dramatically thomas edison switched world 's first large scale electric power


network provided volts direct current dc customers manhattan island new york city sir charles parsons invented steam turbine allowing efficient electric power generation alternating current ability transmit power efficiently long distances via use transformers developed rapidly transformer designs k roly zipernowsky ott bl thy miksa ri later called zbd transformers lucien gaulard john dixon gibbs william stanley jr practical ac motor designs including induction motors independently invented galileo ferraris nikola


tesla developed practical three phase form mikhail dolivo dobrovolsky charles eugene lancelot brown charles steinmetz oliver heaviside contributed theoretical basis alternating current engineering spread use ac set united states called ''war currents'' george westinghouse backed ac system thomas edison backed dc power system ac adopted overall standard early th century guglielmo marconi known pioneering work long distance radio transmission development radio many scientists inventors contributed


radio technology electronics mathematical work james clerk maxwell shown relationship different forms electromagnetic radiation including possibility invisible airborne waves later called radio waves classic physics experiments heinrich hertz proved maxwell 's theory transmitting radio waves spark gap transmitter detected using simple electrical devices physicists experimented new waves process developed devices transmitting detecting guglielmo marconi began work way adapt known methods transmitting detecting


hertzian waves purpose built commercial wireless telegraphic system early sent wireless signals distance one half miles december sent wireless waves affected curvature earth marconi later transmitted wireless signals across atlantic poldhu cornwall st john 's newfoundland distance millimetre wave communication first investigated jagadish chandra bose reached extremely high frequency ghz experiments also introduced use semiconductor junctions detect radio


waves ref name emerson reprinted igor grigorov ed '' https booksgooglecom booksid zsv ih mc antentop '' vol pp ref patented radio crystal detector ref name computerhistory timeline ref ref name computerhistory ref karl ferdinand braun introduced cathode ray tube part oscilloscope crucial enabling technology electronic television john fleming invented first radio tube diode two years later robert von lieben lee de forest independently developed amplifier tube called triode albert hull developed magnetron would eventually lead development microwave oven percy spencer


british military began make strides toward radar also uses magnetron direction dr wimperis culminating operation first radar station bawdsey august konrad zuse presented z world 's first fully functional programmable computer using electromechanical parts tommy flowers designed built colossus world 's first fully functional electronic digital programmable computer eniac electronic numerical integrator computer john presper eckert john mauchly followed beginning computing era arithmetic performance machines


allowed engineers develop completely new technologies achieve new objectives claude shannon publishes mathematical theory communication mathematically describes passage information uncertainty electrical noise solid state electronics replica first working transistor point contact transistor metal oxide semiconductor field effect transistor mosfet basic building block modern electronics first working transistor point contact transistor invented john bardeen walter houser brattain working william shockley bell telephone laboratories btl invented bipolar junction transistor early junction transistors relatively


bulky devices difficult manufacture mass production basis ref name moskowitz ref opened door compact devices surface passivation process electrically stabilized silicon surfaces via thermal oxidation developed mohamed atalla btl led development monolithic integrated circuit chip ref name bassett ref ref name sah considered successful effort bell labs group led atalla stabilize silicon surface important significant technology advance blazed trail led silicon integrated circuit technology developments second phase volume production


mosfet basic element modern electronic equipment ref name nytimescom ref ref name colinge ref central electronics revolution microelectronics revolution ref name zimbovskaya ref digital revolution ref name triumph ref name raymer ref ref name wong ref mosfet thus credited birth modern electronics possibly important invention electronics mosfet made possible build high density integrated circuit chips ref name computerhistory transistor atalla first proposed concept mos integrated circuit mos ic chip followed kahng ref name moskowitz ref name bassett ref earliest experimental mos ic chip fabricated built fred heiman


landing astronauts moon apollo enabled nasa 's adoption advances semiconductor electronic technology including mosfets interplanetary monitoring platform imp silicon integrated circuit chips apollo guidance computer agc development mos integrated circuit technology led invention microprocessor early ref name computerhistory ref ref name colinge first single chip microprocessor intel released ref name computerhistory began busicom project ref name ieee federico faggin http ieeexploreieeeorg stamp stampjsparnumber making first microprocessor ''ieee solid state circuits magazine'' winter ieee xplore ref


masatoshi shima 's three chip cpu design ref name tout ref ref name ieee sharp 's tadashi sasaki conceived single chip cpu design discussed busicom intel ref name sasaki ref intel designed realized federico faggin intel silicon gate mos technology ref name computerhistory along intel 's marcian hoff stanley mazor busicom 's masatoshi shima ref name ieee microprocessor led development microcomputers personal computers microcomputer revolution subfields one properties electricity useful energy transmission well information transmission


also first areas electrical engineering developed today electrical engineering many subdisciplines common listed although electrical engineers focus exclusively one subdisciplines many deal combination sometimes certain fields electronic engineering computer engineering considered disciplines right power energy power pole power energy engineering deals generation transmission distribution electricity well design range related devices include transformers electric generators electric motors high voltage engineering


power electronics many regions world governments maintain electrical network called power grid connects variety generators together users energy users purchase electrical energy grid avoiding costly exercise generate power engineers may work design maintenance power grid well power systems connect ref name unesco systems called ''on grid'' power systems may supply grid additional power draw power grid power engineers may also work


systems connect grid called ''off grid'' power systems cases preferable grid systems future includes satellite controlled power systems feedback real time prevent power surges prevent blackouts telecommunications satellite dishes crucial component analysis satellite information telecommunications engineering focuses transmission information across communication channel coax cable optical fiber free space transmissions across free space require information encoded carrier signal shift information carrier frequency suitable transmission


known modulation popular analog modulation techniques include amplitude modulation frequency modulation choice modulation affects cost performance system two factors must balanced carefully engineer transmission characteristics system determined telecommunication engineers design transmitters receivers needed systems two sometimes combined form two way communication device known transceiver key consideration design transmitters power consumption closely related signal strength typically power transmitted


signal insufficient signal arrives receiver 's antenna information contained signal corrupted noise specifically static control engineering control systems play critical role spaceflight control engineering focuses modeling diverse range dynamic systems design controllers cause systems behave desired manner implement controllers electronics control engineers may use electronic circuits digital signal processors microcontrollers programmable logic controllers plcs control engineering wide range applications flight propulsion systems commercial airliners


cruise control present many modern automobiles also plays important role industrial automation control engineers often use feedback designing control systems example automobile cruise control vehicle 's speed continuously monitored fed back system adjusts motor 's power output accordingly regular feedback control theory used determine system responds feedback control engineers also work robotics design autonomous systems using control algorithms interpret sensory feedback control actuators move robots autonomous vehicles


autonomous drones others used variety industries electronics electronic components electronic engineering involves design testing electronic circuits use properties components resistors capacitors inductors diodes transistors achieve particular functionality ref name unesco ref tuned circuit allows user radio filter single station one example circuit another example research pneumatic signal conditioner prior second world war subject commonly known ''radio engineering'' basically restricted aspects communications


radar commercial radio early television ref name unesco later post war years consumer devices began developed field grew include modern television audio systems computers microprocessors mid late term ''radio engineering'' gradually gave way name ''electronic engineering'' invention integrated circuit electronic circuits constructed discrete components could manipulated humans discrete circuits consumed much space power limited speed although still common applications contrast integrated circuits packed large number often millions tiny


electrical components mainly transistors small chip around size coin allowed powerful computers electronic devices see today microelectronics nanoelectronics microprocessor microelectronics engineering deals design microfabrication small electronic circuit components use integrated circuit sometimes use general electronic component common microelectronic components semiconductor transistors although main electronic components resistors capacitors etc created microscopic level nanoelectronics scaling devices nanometer levels modern devices


already nanometer regime nbsp nm processing standard since around microelectronic components created chemically fabricating wafers semiconductors silicon higher frequencies compound semiconductors like gallium arsenide indium phosphide obtain desired transport electronic charge control current field microelectronics involves significant amount chemistry material science requires electronic engineer working field good working knowledge effects quantum mechanics signal processing bayer filter ccd requires signal processing get


red green blue value pixel signal processing deals analysis manipulation signals signals either analog case signal varies continuously according information digital case signal varies according series discrete values representing information analog signals signal processing may involve amplification filtering audio signals audio equipment modulation demodulation signals telecommunications digital signals signal processing may involve compression error detection error correction digitally sampled signals signal processing


mathematically oriented intensive area forming core digital signal processing rapidly expanding new applications every field electrical engineering communications control radar audio engineering broadcast engineering power electronics biomedical engineering many already existing analog systems replaced digital counterparts analog signal processing still important design many control systems dsp processor ics found many types modern electronic devices digital television sets radios hi fi audio equipment mobile phones multimedia players camcorders digital cameras automobile control systems noise cancelling


headphones digital spectrum analyzers missile guidance systems radar systems telematics systems products dsp may responsible noise reduction speech recognition synthesis encoding decoding digital media wirelessly transmitting receiving data triangulating positions using gps kinds image processing video processing audio processing speech processing instrumentation flight instruments provide pilots tools control aircraft analytically instrumentation engineering deals design devices measure physical quantities pressure flow temperature design instruments requires good understanding physics often extends beyond electromagnetic theory


example flight instruments measure variables wind speed altitude enable pilots control aircraft analytically similarly thermocouples use peltier seebeck effect measure temperature difference two points often instrumentation used instead sensors larger electrical systems example thermocouple might used help ensure furnace 's temperature remains constant reason instrumentation engineering often viewed counterpart control computers supercomputers used fields diverse computational biology geographic information systems computer engineering deals design


computers computer systems may involve design new hardware design pdas tablets supercomputers use computers control industrial plant computer engineers may also work system 's software however design complex software systems often domain software engineering usually considered separate discipline desktop computers represent tiny fraction devices computer engineer might work computer like architectures found range devices including video game consoles dvd players computer engineers involved many hardware


bird vip infant ventilator mechatronics engineering discipline deals convergence electrical mechanical systems combined systems known electromechanical systems widespread adoption examples include automated manufacturing systems heating ventilation air conditioning systems various subsystems aircraft automobiles ''electronic systems design'' subject within electrical engineering deals multi disciplinary design issues complex electrical mechanical systems ref name lienig ref term ''mechatronics'' typically used refer macroscopic systems futurists predicted emergence small electromechanical devices already small devices known microelectromechanical


systems mems used automobiles tell airbags deploy digital projectors create sharper images inkjet printers create nozzles high definition printing future hoped devices help build tiny implantable medical devices improve optical communication biomedical engineering another related discipline concerned design medical equipment includes fixed equipment ventilators mri scanners electrocardiograph monitors well mobile equipment cochlear implants artificial pacemakers artificial hearts aerospace engineering robotics example recent electric propulsion


ion propulsion education oscilloscope electrical engineers typically possess academic degree major electrical engineering electronics engineering electrical engineering technology ref name bls ref electrical electronic engineering fundamental principles taught programs though emphasis may vary according title length study degree usually four five years completed degree may designated bachelor science electrical electronics engineering technology bachelor engineering bachelor science bachelor technology bachelor applied science depending university bachelor 's degree generally includes units covering


physics mathematics computer science project management variety topics electrical engineering ref name enterprise ref initially topics cover subdisciplines electrical engineering schools students choose emphasize one subdisciplines towards end courses study example circuit diagram useful circuit design troubleshooting many schools electronic engineering included part electrical award sometimes explicitly bachelor engineering electrical electronic others electrical electronic engineering considered sufficiently


broad complex separate degrees offered electrical engineers choose study postgraduate degree master engineering master science meng msc master engineering management doctor philosophy phd engineering engineering doctorate engd engineer 's degree master 's engineer 's degrees may consist either research coursework mixture two doctor philosophy engineering doctorate degrees consist significant research component often viewed entry point academia united kingdom european countries master engineering


often considered undergraduate degree slightly longer duration bachelor engineering rather standalone postgraduate degree professional practice belgian electrical engineers inspecting rotor kilowatt turbine general electric company new york city countries bachelor 's degree engineering represents first step towards professional certification degree program certified professional body ref name labor ref completing certified degree program engineer must satisfy range requirements including work experience requirements certified certified engineer designated


title professional engineer united states canada south africa chartered engineer incorporated engineer india pakistan united kingdom ireland zimbabwe chartered professional engineer australia new zealand european engineer much european union ieee corporate office th floor park avenue new york city advantages licensure vary depending upon location example united states canada licensed engineer may seal engineering work public private clients requirement enforced state provincial legislation


quebec 's engineers act countries legislation exists practically certifying bodies maintain code ethics expect members abide risk expulsion way organizations play important role maintaining ethical standards profession even jurisdictions certification little legal bearing work engineers subject contract law cases engineer 's work fails may subject tort negligence extreme cases charge criminal negligence engineer 's work must also comply numerous


rules regulations building codes legislation pertaining environmental law professional bodies note electrical engineers include institute electrical electronics engineers ieee institution engineering technology iet ieee claims produce world 's literature electrical engineering members worldwide holds conferences annually iet publishes journals worldwide membership claims largest professional engineering society europe obsolescence technical skills serious concern electrical engineers membership participation


technical societies regular reviews periodicals field habit continued learning therefore essential maintaining proficiency miet member institution engineering technology recognised europe electrical computer technology engineer australia canada united states electrical engineers make around labor force ref australia around canada around constituting labour force three countries australia canada reported electrical engineers respectively


male tools work global positioning system electric power generation electrical engineers contributed development wide range technologies design develop test supervise deployment electrical systems electronic devices example may work design telecommunication systems operation electric power stations lighting wiring buildings design household appliances electrical control industrial machinery satellite communications typical electrical engineers work fundamental discipline sciences physics mathematics help


obtain qualitative quantitative description systems work today engineering work involves use computers commonplace use computer aided design programs designing electrical systems nevertheless ability sketch ideas still invaluable quickly communicating others shadow robot hand system although electrical engineers understand basic circuit theory interactions elements resistors capacitors diodes transistors inductors circuit theories employed engineers generally depend upon work example quantum mechanics solid state physics might


relevant engineer working vlsi design integrated circuits largely irrelevant engineers working macroscopic electrical systems even circuit theory may relevant person designing telecommunication systems use shelf components perhaps important technical skills electrical engineers reflected university programs emphasize strong numerical skills computer literacy ability understand technical language concepts relate electrical engineering laser bouncing acrylic rod illustrating total internal reflection light multi mode optical fiber wide range


instrumentation used electrical engineers simple control circuits alarms basic multimeter measuring voltage current resistance may suffice time varying signals need studied oscilloscope also ubiquitous instrument rf engineering high frequency telecommunications spectrum analyzers network analyzers used disciplines safety particular concern instrumentation instance medical electronics designers must take account much lower voltages normal dangerous electrodes directly contact internal body fluids power transmission engineering also great


safety concerns due high voltages used although voltmeters may principle similar low voltage equivalents safety calibration issues make different many disciplines electrical engineering use tests specific discipline audio electronics engineers use audio test sets consisting signal generator meter principally measure level also parameters harmonic distortion noise likewise information technology test sets often specific particular data format true television broadcasting radome misawa air base misawa


security operations center misawa japan many engineers technical work accounts fraction work lot time may also spent tasks discussing proposals clients preparing budgets determining project schedules many senior engineers manage team technicians engineers reason project management skills important engineering projects involve form documentation strong written communication skills therefore important workplaces engineers varied types work electrical engineers may found


pristine lab environment fabrication plant board naval ship offices consulting firm site mine working life electrical engineers may find supervising wide range individuals including scientists electricians computer programmers engineers electrical engineering intimate relationship physical sciences instance physicist lord kelvin played major role engineering first transatlantic telegraph cable conversely engineer oliver heaviside produced major work mathematics transmission telegraph cables electrical engineers often required


major science projects instance large particle accelerators cern need electrical engineers deal many aspects project including power distribution instrumentation manufacture installation superconducting electromagnets see also barnacle slang electrical technologist electronic design automation glossary electrical electronics engineering index electrical engineering articles information engineering international electrotechnical commission iec list electrical engineers list engineering branches list mechanical electrical electronic equipment manufacturing companies revenue list russian electrical engineers occupations electrical electronics engineering outline electrical engineering timeline electrical


electronic engineering notes references bibliography martini l bscco multilayered conductors ''superconducting materials high energy colliders'' pp nbsp world scientific schmidt r diger lhc accelerator challenges kramer soler fjp eds ''large hadron collider phenomenology'' pp nbsp crc press reading external links http wwwiecch international electrotechnical commission iec http ocwmitedu ocwweb electrical engineering computer science indexhtm mit opencourseware depth look electrical engineering online courses video lectures http wwwieeeghnorg ieee global history network wiki based site many resources history ieee members professions electrical informational technologies sciences electronic engineering computer engineering electrical


computer engineering engineering disciplines


regions electromagnetic phenomena defined terms electromagnetic force sometimes called lorentz force includes electricity magnetism different manifestations phenomenon electromagnetic force plays major role determining internal properties objects encountered daily life electromagnetic attraction atomic nuclei orbital electrons holds atoms together electromagnetic forces responsible chemical bonds atoms create molecules intermolecular forces electromagnetic force governs chemical processes arise interactions electrons neighboring atoms electromagnetism

Natural science
Physics
Electromagnetism


widely used modern technology electromagnetic theory basis electric power engineering electronics including digital technology numerous mathematical descriptions electromagnetic field prominently maxwell 's equations describe electric magnetic fields generated altered charges currents theoretical implications electromagnetism particularly establishment speed light based properties medium propagation permeability permittivity led development special relativity albert einstein history theory hans christian rsted originally electricity magnetism


another manner similar positive negative charges always exist pairs every north pole yoked south pole electric current inside wire creates corresponding circumferential magnetic field outside wire direction clockwise counter clockwise depends direction current wire current induced loop wire moved toward away magnetic field magnet moved towards away direction current depends movement andr marie amp


findings resulted intensive research throughout scientific community electrodynamics influenced french physicist andr marie amp 's developments single mathematical form represent magnetic forces current carrying conductors rsted 's discovery also represented major step toward unified concept energy unification observed michael faraday extended james clerk maxwell partially reformulated oliver heaviside heinrich hertz one key accomplishments th century mathematical physics far reaching consequences one understanding nature light unlike proposed electromagnetic theory


time light electromagnetic waves present seen taking form quantized self propagating oscillatory electromagnetic field disturbances called photons different frequencies oscillation give rise different forms electromagnetic radiation radio waves lowest frequencies visible light intermediate frequencies gamma rays highest frequencies rsted person examine relationship electricity magnetism gian domenico romagnosi italian legal scholar deflected magnetic needle using voltaic pile factual setup experiment completely clear


current flowed across needle account discovery published italian newspaper largely overlooked contemporary scientific community romagnosi seemingly belong community earlier often neglected connection electricity magnetism reported dr cookson account stated blockquote tradesman wakefield yorkshire put great number knives forks large box placed box corner large room happened sudden storm thunder


lightning c owner emptying box counter nails lay persons took knives lay nails observed knives took nails whole number tried found degree take large nails packing needles iron things considerable weight blockquote e whittaker suggested particular event responsible lightning credited power magnetizing steel doubtless


led franklin attempt magnetize sewing needle means discharge leyden jars fundamental forces representation electric field vector wave circularly polarized electromagnetic radiation electromagnetic force one four known fundamental forces fundamental forces strong nuclear force binds quarks form nucleons binds nucleons form nuclei weak nuclear force binds known particles standard model causes certain forms radioactive decay particle physics though electroweak interaction unified description


two four known fundamental interactions nature electromagnetism weak interaction gravitational force forces eg friction contact forces derived four fundamental forces known non fundamental forces electromagnetic force responsible practically phenomena one encounters daily life nuclear scale exception gravity roughly speaking forces involved interactions atoms explained electromagnetic force acting electrically charged atomic nuclei electrons atoms electromagnetic forces also explain particles carry momentum


movement includes forces experience pushing pulling ordinary material objects result intermolecular forces act individual molecules bodies objects electromagnetic force also involved forms chemical phenomena necessary part understanding intra atomic intermolecular forces effective force generated momentum electrons' movement electrons move interacting atoms carry momentum collection electrons becomes confined minimum momentum necessarily increases due pauli


exclusion principle behaviour matter molecular scale including density determined balance electromagnetic force force generated exchange momentum carried electrons classical electrodynamics william gilbert proposed ''de magnete'' electricity magnetism capable causing attraction repulsion objects distinct effects mariners noticed lightning strikes ability disturb compass needle link lightning electricity confirmed benjamin franklin 's proposed experiments one first


discover publish link man made electric current magnetism gian romagnosi noticed connecting wire across voltaic pile deflected nearby compass needle however effect become widely known rsted performed similar experiment ref name 'oersted' ref rsted 's work influenced amp produce theory electromagnetism set subject mathematical foundation theory electromagnetism known classical electromagnetism developed various physicists period culminated publication treatise james clerk maxwell


unified preceding developments single theory discovered electromagnetic nature light classical electromagnetism behavior electromagnetic field described set equations known maxwell 's equations electromagnetic force given lorentz force law one peculiarities classical electromagnetism difficult reconcile classical mechanics compatible special relativity according maxwell 's equations speed light vacuum universal constant dependent electrical permittivity magnetic permeability free space


violates galilean invariance long standing cornerstone classical mechanics one way reconcile two theories electromagnetism classical mechanics assume existence luminiferous aether light propagates however subsequent experimental efforts failed detect presence aether important contributions hendrik lorentz henri poincar albert einstein solved problem introduction special relativity replaced classical kinematics new theory kinematics compatible classical electromagnetism information see history special relativity addition relativity theory implies moving frames


nonlinear dynamics occur electromagnetic fields couple matter follows nonlinear dynamical laws studied example subject magnetohydrodynamics combines maxwell theory navier stokes equations quantities units '''electromagnetic units''' part system electrical units based primarily upon magnetic properties electric currents fundamental si unit ampere units ampere electric current coulomb electric charge farad capacitance henry inductance ohm resistance siemens conductance tesla magnetic flux density volt electric potential watt power weber magnetic flux electromagnetic cgs system electric current


fundamental quantity defined via amp 's law takes permeability dimensionless quantity relative permeability whose value vacuum unity consequence square speed light appears explicitly equations interrelating quantities system formulas physical laws electromagnetism maxwell 's equations need adjusted depending system units one uses one one correspondence electromagnetic units si cgs case mechanical units furthermore within cgs several plausible choices


lightning one dramatic effects electricity '''electricity''' set physical phenomena associated presence motion matter property electric charge electricity related magnetism part phenomenon electromagnetism described maxwell 's equations various common phenomena related electricity including lightning static electricity electric heating electric discharges many others presence electric charge either positive negative produces electric field movement electric charges electric current produces magnetic field


charge placed location non zero electric field force act magnitude force given coulomb 's law charge moves electric field would work electric charge thus speak electric potential certain point space equal work done external agent carrying unit positive charge arbitrarily chosen reference point point without acceleration typically measured volts electricity heart many


society becoming driving force second industrial revolution electricity 's extraordinary versatility means put almost limitless set applications include transport heating lighting communications computation electrical power backbone modern industrial society history thales earliest known researcher electricity long knowledge electricity existed people aware shocks electric fish ancient egyptian texts dating bce referred fish thunderer nile described protectors fish electric fish


reported millennia later ancient greek roman arabic naturalists physicians several ancient writers pliny elder scribonius largus attested numbing effect electric shocks delivered electric catfish electric rays knew shocks could travel along conducting objects ref name electroreception ref patients suffering ailments gout headache directed touch electric fish hope powerful jolt might cure ref name morris ref ancient cultures around mediterranean knew certain objects rods amber could rubbed cat 's fur attract light


nature benjamin franklin conducted extensive research electricity th century documented joseph priestley ''history present status electricity'' franklin carried extended correspondence electricity would remain little intellectual curiosity millennia english scientist william gilbert wrote ''de magnete'' made careful study electricity magnetism distinguishing lodestone effect static electricity produced rubbing amber ref name stewart coined new latin word ''electricus'' amber like amber ''elektron'' greek word amber refer


property attracting small objects rubbed association gave rise english words electric electricity made first appearance print thomas browne 's ''pseudodoxia epidemica'' work conducted th early th centuries otto von guericke robert boyle stephen gray c f du fay ref name guarnieri ref later th century benjamin franklin conducted extensive research electricity selling possessions fund work june reputed attached metal key bottom dampened kite string flown


kite storm threatened sky succession sparks jumping key back hand showed lightning indeed electrical nature also explained apparently paradoxical behavior leyden jar device storing large amounts electrical charge terms electricity consisting positive negative charges ref name guarnieri michael faraday 's discoveries formed foundation electric motor technology luigi galvani published discovery bioelectromagnetics demonstrating electricity medium neurons passed signals muscles ref name guarnieri ref ref name kirby ref ref name guarnieri


alessandro volta 's battery voltaic pile made alternating layers zinc copper provided scientists reliable source electrical energy electrostatic machines previously used ref name guarnieri ref name kirby recognition electromagnetism unity electric magnetic phenomena due hans christian rsted andr marie amp michael faraday invented electric motor georg ohm mathematically analysed electrical circuit ref name kirby electricity magnetism light definitively linked james clerk maxwell particular physical lines force


early th century seen rapid progress electrical science late th century would see greatest progress electrical engineering people alexander graham bell ott bl thy thomas edison galileo ferraris oliver heaviside nyos jedlik william thomson st baron kelvin charles algernon parsons werner von siemens joseph swan reginald fessenden nikola tesla george westinghouse electricity turned scientific curiosity essential tool modern life heinrich hertz ref name uniphysics ref name hertz ref discovered electrodes illuminated ultraviolet light create electric sparks easily albert einstein published


paper explained experimental data photoelectric effect result light energy carried discrete quantized packets energising electrons discovery led quantum revolution einstein awarded nobel prize physics discovery law photoelectric effect photoelectric effect also employed photocells found solar panels frequently used make electricity commercially first solid state device cat 's whisker detector first used radio receivers whisker like wire placed lightly contact


solid crystal germanium crystal detect radio signal contact junction effect solid state component current confined solid elements compounds engineered specifically switch amplify current flow understood two forms negatively charged electrons positively charged electron deficiencies called holes charges holes understood terms quantum physics building material often crystalline semiconductor solid state electronics came emergence transistor technology first working transistor germanium based point contact transistor


transition vacuum tubes semiconductor diodes transistors integrated circuit ic chips mosfets light emitting diode led technology common electronic device mosfet ref name computerhistory transistor ref name golio ref become widely manufactured device history ref name computerhistory ref common solid state mos devices include microprocessor chips ref name ieee ref semiconductor memory special type semiconductor memory flash memory used usb flash drives mobile devices well solid state drive ssd technology replace mechanically rotating magnetic disc hard disk drive hdd technology concepts electric charge charge gold leaf electroscope causes leaves


however one ball charged glass rod amber rod two balls found attract phenomena investigated late eighteenth century charles augustin de coulomb deduced charge manifests two opposing forms discovery led well known axiom ''like charged objects repel opposite charged objects attract'' ref name uniphysics force acts charged particles hence charge tendency spread evenly possible conducting surface magnitude electromagnetic force whether attractive repulsive


given coulomb 's law relates force product charges inverse square relation distance ref name duffin ref electromagnetic force strong second strength strong interaction unlike force operates distances ref name umashankar ref comparison much weaker gravitational force electromagnetic force pushing two electrons apart sup sup times gravitational attraction pulling together ref name hawking ref charge originates certain types subatomic particles familiar carriers electron proton electric


charge gives rise interacts electromagnetic force one four fundamental forces nature experiment shown charge conserved quantity net charge within electrically isolated system always remain constant regardless changes taking place within system within system charge may transferred bodies either direct contact passing along conducting material wire ref name duffin informal term static electricity refers net presence 'imbalance' charge body usually caused dissimilar materials rubbed together


transferring charge one charge electrons protons opposite sign hence amount charge may expressed either negative positive convention charge carried electrons deemed negative protons positive custom originated work benjamin franklin amount charge usually given symbol ''q'' expressed coulombs electron carries charge approximately sup sup nbsp coulomb proton charge equal opposite thus sup sup nbsp coulomb charge possessed matter


also antimatter antiparticle bearing equal opposite charge corresponding particle charge measured number means early instrument gold leaf electroscope although still use classroom demonstrations superseded electronic electrometer ref name duffin electric current movement electric charge known electric current intensity usually measured amperes current consist moving charged particles commonly electrons charge motion constitutes current electric current flow things electrical conductors


move quite slowly sometimes average drift velocity fractions millimetre per second ref name duffin electric field drives propagates close speed light enabling electrical signals pass rapidly along wires current causes several observable effects historically means recognising presence water could decomposed current voltaic pile discovered nicholson carlisle process known electrolysis work greatly expanded upon michael faraday current resistance causes localised heating effect


james prescott joule studied mathematically ref name duffin one important discoveries relating current made accidentally hans christian rsted preparing lecture witnessed current wire disturbing needle magnetic compass ref name berkson accounts differ whether lecture ref discovered electromagnetism fundamental interaction electricity magnetics level electromagnetic emissions generated electric arcing high enough produce electromagnetic interference detrimental workings adjacent equipment engineering household


applications current often described either direct current dc alternating current ac terms refer current varies time direct current produced example battery required electronic devices unidirectional flow positive part circuit negative ref name bird ref common flow carried electrons travelling opposite direction alternating current current reverses direction repeatedly almost always takes form sine wave ref name bird alternating current thus pulses back


forth within conductor without charge moving net distance time time averaged value alternating current zero delivers energy first one direction reverse alternating current affected electrical properties observed steady state direct current inductance capacitance ref name bird properties however become important circuitry subjected transients first energised electric field concept electric field introduced michael faraday electric field created charged body space


surrounds results force exerted charges placed within field electric field acts two charges similar manner way gravitational field acts two masses like extends towards infinity shows inverse square relationship distance ref name umashankar however important difference gravity always acts attraction drawing two masses together electric field result either attraction repulsion since large bodies planets generally carry net charge electric field distance usually zero thus


gravity dominant force distance universe despite much weaker ref name hawking field lines emanating positive charge plane conductor electric field generally varies space strength one point defined force per unit charge would felt stationary negligible charge placed point ref name uniphysics conceptual charge termed 'test charge' must vanishingly small prevent electric field disturbing main field must also stationary prevent effect magnetic fields electric field


defined terms force force vector magnitude direction follows electric field vector field ref name uniphysics study electric fields created stationary charges called electrostatics field may visualised set imaginary lines whose direction point field concept introduced faraday ref name elec princ p ref whose term 'lines force' still sometimes sees use field lines paths point positive charge would seek make forced


move within field however imaginary concept physical existence field permeates intervening space lines ref name elec princ p field lines emanating stationary charges several key properties first originate positive charges terminate negative charges second must enter good conductor right angles third may never cross close ref name uniphysics hollow conducting body carries charge outer surface field therefore zero places inside body ref name duffin


operating principal faraday cage conducting metal shell isolates interior outside electrical effects principles electrostatics important designing items high voltage equipment finite limit electric field strength may withstood medium beyond point electrical breakdown occurs electric arc causes flashover charged parts air example tends arc across small gaps electric field strengths exceed nbsp kv per centimetre larger gaps breakdown strength weaker perhaps nbsp kv per centimetre ref name hv eng ref visible natural occurrence


lightning caused charge becomes separated clouds rising columns air raises electric field air greater withstand voltage large lightning cloud may high nbsp mv discharge energies great nbsp kwh field strength greatly affected nearby conducting objects particularly intense forced curve around sharply pointed objects principle exploited lightning conductor sharp spike acts encourage lightning stroke develop rather


stated ref name uniphysics volt strongly identified unit choice measurement description electric potential difference term voltage sees greater everyday usage practical purposes useful define common reference point potentials may expressed compared could infinity much useful reference earth assumed potential everywhere reference point naturally takes name earth ground earth assumed infinite source equal amounts positive negative charge


therefore electrically uncharged unchargeable electric potential scalar quantity magnitude direction may viewed analogous height released object fall difference heights caused gravitational field charge 'fall' across voltage caused electric field relief maps show contour lines marking points equal height set lines marking points equal potential known equipotentials may drawn around electrostatically charged object equipotentials cross lines force right angles


force rsted fully understand discovery observed effect reciprocal current exerts force magnet magnetic field exerts force current phenomenon investigated amp discovered two parallel current carrying wires exerted force upon two wires conducting currents direction attracted wires containing currents opposite directions forced apart ref name elec princ ref interaction mediated magnetic field current produces forms basis international definition


ampere ref name elec princ electric motor exploits important effect electromagnetism current magnetic field experiences force right angles field current relationship magnetic fields currents extremely important led michael faraday 's invention electric motor faraday 's homopolar motor consisted permanent magnet sitting pool mercury current allowed wire suspended pivot magnet dipped mercury magnet exerted tangential force wire making circle around


magnet long current maintained ref name iet faraday ref experimentation faraday revealed wire moving perpendicular magnetic field developed potential difference ends analysis process known electromagnetic induction enabled state principle known faraday 's law induction potential difference induced closed circuit proportional rate change magnetic flux loop exploitation discovery enabled invent first electrical generator converted mechanical energy


rotating copper disc electrical energy ref name iet faraday faraday 's disc inefficient use practical generator showed possibility generating electric power using magnetism possibility would taken followed work electrochemistry italian physicist alessandro volta showing '' battery '' french emperor napoleon bonaparte early th century ability chemical reactions produce electricity conversely ability electricity drive chemical reactions wide array uses electrochemistry always important part electricity initial invention


voltaic pile electrochemical cells evolved many different types batteries electroplating electrolysis cells aluminium produced vast quantities way many portable devices electrically powered using rechargeable cells electric circuits basic electric circuit voltage source ''v'' left drives current ''i'' around circuit delivering electrical energy resistor ''r'' resistor current returns source completing circuit electric circuit interconnection electric components electric charge made flow along closed path circuit usually


produce potential difference one volt response current one amp ref name alexander capacitor development leyden jar device store charge thereby storing electrical energy resulting field consists two conducting plates separated thin insulating dielectric layer practice thin metal foils coiled together increasing surface area per unit volume therefore capacitance unit capacitance farad named michael faraday given symbol ''f'' one farad capacitance develops potential


induced voltage proportional time rate change current constant proportionality termed inductance unit inductance henry named joseph henry contemporary faraday one henry inductance induce potential difference one volt current changes rate one ampere per second inductor 's behaviour regards converse capacitor freely allow unchanging current opposes rapidly changing one ref name alexander electric power electric power rate


electric energy transferred electric circuit si unit power watt one joule per second electric power like mechanical power rate work measured watts represented letter ''p'' term ''wattage'' used colloquially mean electric power watts electric power watts produced electric current ''i'' consisting charge ''q'' coulombs every ''t'' seconds passing electric potential voltage difference ''v'' math p text work done per unit time frac qv iv math ''q'' electric


charge coulombs ''t'' time seconds ''i'' electric current amperes ''v'' electric potential voltage volts electricity generation often done process converting mechanical energy electricity devices steam turbines gas turbines involved production mechanical energy passed electric generators produce electricity electricity also supplied chemical sources electric batteries means wide variety sources energy electric power generally supplied businesses homes electric


power industry electricity usually sold kilowatt hour mj product power kilowatts multiplied running time hours electric utilities measure power using electricity meters keep running total electric energy delivered customer unlike fossil fuels electricity low entropy form energy converted motion many forms energy high efficiency electronics surface mount electronic components electronics deals electrical circuits involve active electrical components vacuum tubes transistors diodes optoelectronics sensors integrated circuits associated


passive interconnection technologies nonlinear behaviour active components ability control electron flows makes amplification weak signals possible electronics widely used information processing telecommunications signal processing ability electronic devices act switches makes digital information processing possible interconnection technologies circuit boards electronics packaging technology varied forms communication infrastructure complete circuit functionality transform mixed components regular working system today electronic devices use semiconductor components perform electron control study semiconductor devices related technology considered branch


developed set equations could unambiguously describe interrelationship electric field magnetic field electric charge electric current could moreover prove wave would necessarily travel speed light thus light form electromagnetic radiation maxwell 's laws unify light fields charge one great milestones theoretical physics ref name uniphysics thus work many researchers enabled use electronics convert signals high frequency oscillating currents via suitably shaped conductors electricity permits transmission reception signals via radio


electricity became available voltaic pile modern descendant electrical battery store energy chemically make available demand form electrical energy ref name batteries battery versatile common power source ideally suited many applications energy storage finite discharged must disposed recharged large electrical demands electrical energy must generated transmitted continuously conductive transmission lines electrical power usually generated electro mechanical generators driven steam produced fossil fuel combustion heat released nuclear


reactions sources kinetic energy extracted wind flowing water modern steam turbine invented sir charles parsons today generates percent electric power world using variety heat sources generators bear resemblance faraday 's homopolar disc generator still rely electromagnetic principle conductor linking changing magnetic field induces potential difference across ends invention late nineteenth century transformer meant electrical power could transmitted efficiently


higher voltage lower current efficient electrical transmission meant turn electricity could generated centralised power stations benefited economies scale despatched relatively long distances needed ref name patterson p ref wind power increasing importance many countries since electrical energy cannot easily stored quantities large enough meet demands national scale times exactly much must produced required ref name patterson p requires electricity utilities make careful predictions electrical loads maintain constant co ordination power


led increased focus generation renewable sources particular wind solar debate expected continue environmental impact different means electricity production final form relatively clean ref name nrc applications light bulb early application electricity operates joule heating passage current resistance generating heat electricity convenient way transfer energy adapted huge growing number uses invention practical incandescent light bulb led lighting becoming one


first publicly available applications electrical power although electrification brought dangers replacing naked flames gas lighting greatly reduced fire hazards within homes factories public utilities set many cities targeting burgeoning market electrical lighting late th century modern times trend started flow direction deregulation electrical power sector resistive joule heating effect employed filament light bulbs also sees direct use electric heating versatile controllable seen wasteful


since electrical generation already required production heat power station number countries denmark issued legislation restricting banning use resistive electric heating new buildings electricity however still highly practical energy source heating refrigeration air conditioning heat pumps representing growing sector electricity demand heating cooling effects electricity utilities increasingly obliged accommodate electricity used within telecommunications indeed electrical telegraph demonstrated commercially cooke wheatstone one earliest applications


construction first transcontinental transatlantic telegraph systems electricity enabled communications minutes across globe optical fibre satellite communication taken share market communications systems electricity expected remain essential part process effects electromagnetism visibly employed electric motor provides clean efficient means motive power stationary motor winch easily provided supply power motor moves application electric


vehicle obliged either carry along power source battery collect current sliding contact pantograph electrically powered vehicles used public transportation electric buses trains increasing number battery powered electric cars private ownership electronic devices make use transistor perhaps one important inventions twentieth century fundamental building block modern circuitry modern integrated circuit may contain several billion miniaturised transistors region centimetres square electricity natural


world physiological effects voltage applied human body causes electric current tissues although relationship non linear greater voltage greater current ref name tleis ref threshold perception varies supply frequency path current nbsp nbsp mains frequency electricity though current low microamp detected electrovibration effect certain conditions current sufficiently high cause muscle contraction fibrillation heart tissue burns ref name tleis lack visible


sign conductor electrified makes electricity particular hazard pain caused electric shock intense leading electricity times employed method torture death caused electric shock referred electrocution electrocution still means judicial execution jurisdictions though use become rarer recent times electrical phenomena nature electric eel ''electrophorus electricus'' electricity human invention may observed several forms nature prominent manifestation lightning many interactions familiar


macroscopic level touch friction chemical bonding due interactions electric fields atomic scale earth 's magnetic field thought arise natural dynamo circulating currents planet 's core certain crystals quartz even sugar generate potential difference across faces subjected external pressure ref name crystallography ref phenomenon known piezoelectricity greek ''piezein'' meaning press discovered pierre jacques curie effect reciprocal piezoelectric material subjected electric field


life many people even industrialised western world popular culture time accordingly often depicted mysterious quasi magical force slay living revive dead otherwise bend laws nature ref name van riper ref attitude began experiments luigi galvani legs dead frogs shown twitch application animal electricity revitalization resuscitation apparently dead drowned persons reported medical literature shortly galvani 's work results known mary shelley authored ''frankenstein''


although name method revitalization monster revitalization monsters electricity later became stock theme horror films public familiarity electricity lifeblood second industrial revolution grew wielders often cast positive light ref name van riper van riper opcit p ref workers finger death gloves' end piece repiece living wires rudyard kipling 's poem ''sons martha'' ref name van riper electrically powered vehicles every sort featured large adventure stories


nameless hero jimmy webb song wichita lineman ref name van riper still often cast heroic wizard like figures ref name van riper see also amp 's circuital law connects direction electric current associated magnetic currents electric potential energy potential energy system charges electricity market sale electrical energy etymology ''electricity'' origin word ''electricity'' current different usages hydraulic analogy analogy flow water electric current notes references benjamin p https archiveorg details ahistoryelectri benjgoog history electricity intellectual rise


electricity antiquity days benjamin franklin new york j wiley sons external links http wwwibiblioorg kuphaldt electriccircuits dc dc html ''basic concepts electricity'' chapter http wwwibiblioorg kuphaldt electriccircuits dc indexhtml ''lessons electric circuits vol dc'' book http wwwibiblioorg kuphaldt electriccircuits series https booksgooglecom booksid n mdaaaambaj pg pa dq popular mechanics curtiss v onepage q f true one hundred years electricity may popular mechanics http wwwhometipscom hyhw electrical electrichtml illustrated view american home 's electrical system works http wwwworldstandardseu electricity plugs sockets electricity around world http amascicom miscon electhtml electricity misconceptions https webarchiveorg web http wwwmicromagnetfsuedu electromag java diode indexhtml electricity magnetism http steverosecom articles understandingbasicelectrihtml understanding electricity electronics minutes http waterworldbankorg water publications water electricity poor benefits utility subsidies world bank report water electricity utility subsidies


john daniell left physicist michael faraday right credited founders electrochemistry today '''electrochemistry''' branch physical chemistry concerned relationship electrical potential measurable quantitative phenomenon identifiable chemical change either electrical potential outcome particular chemical change vice versa reactions involve electrons moving electrodes via electronically conducting phase typically necessarily external electrical circuit electrolessplating separated ionically conducting electronically insulating electrolyte ionic species solution chemical reaction effected

Natural science
Chemistry
Electrochemistry


potential difference electrolysis electrical potential results chemical reaction battery fuel cell called ''electrochemical'' reaction unlike chemical reactions electrochemical reactions electrons necessarily resulting ions transferred directly molecules via aforementioned electronically ionically conducting circuits respectively phenomenon distinguishes electrochemical reaction chemical reaction history german physicist otto von guericke beside electrical generator conducting experiment th th century developments understanding electrical matters began sixteenth century century english scientist william gilbert


spent years experimenting magnetism lesser extent electricity work magnets gilbert became known '' father magnetism '' discovered various methods producing strengthening magnets german physicist otto von guericke created first electric generator produced static electricity applying friction machine generator made large sulfur ball cast inside glass globe mounted shaft ball rotated means crank electric spark produced pad rubbed ball


biological life forms ref name g john robert norris douglas w ribbons https booksgooglecom booksid tffqpqksc ec pg pa methods microbiology volume academic press p ref essay galvani concluded animal tissue contained fore neglected innate vital force termed '' animal electricity '' activated nerves muscles spanned metal probes believed new force form electricity addition '' natural '' form produced lightning electric eel torpedo ray well '' artificial '' form produced friction ie static electricity ref name g frederick collier bakewell https archiveorg details bub gb lks aaaamaaj page n electric science history


phenomena applications ingram cooke pp ref galvani 's scientific colleagues generally accepted views alessandro volta rejected idea '' animal electric fluid '' replying frog 's legs responded differences metal temper composition bulk ref name g ref name g galvani refuted obtaining muscular action two pieces material th century sir humphry davy 's portrait th century william nicholson johann wilhelm ritter succeeded decomposing water hydrogen oxygen electrolysis soon thereafter ritter discovered process electroplating also observed amount metal


deposited amount oxygen produced electrolytic process depended distance electrodes ref name lai ritter observed thermoelectric currents anticipated discovery thermoelectricity thomas johann seebeck william hyde wollaston made improvements galvanic cell sir humphry davy 's work electrolysis led conclusion production electricity simple electrolytic cells resulted chemical action chemical combination occurred substances opposite charge work led directly isolation sodium potassium compounds alkaline earth metals


hans christian rsted 's discovery magnetic effect electric currents immediately recognized epoch making advance although left work electromagnetism others andr marie amp quickly repeated rsted 's experiment formulated mathematically estonian german physicist thomas johann seebeck demonstrated electrical potential juncture points two dissimilar metals heat difference joints ref name ohm brian scott baigrie https booksgooglecom booksid xec xkwxi c pg pa electricity magnetism historical perspective greenwood publishing group p ref german scientist georg ohm expressed law


famous book '' die galvanische kette mathematisch bearbeitet '' galvanic circuit investigated mathematically gave complete theory electricity ref name ohm michael faraday 's experiments led state two laws electrochemistry john daniell invented primary cell solved problem polarization eliminating hydrogen gas generation positive electrode later results revealed alloying amalgamated zinc mercury would produce higher voltage swedish chemist svante arrhenius portrait circa william grove produced first fuel cell wilhelm weber developed electrodynamometer georges


obtain aluminium using electrolysis molten alumina friedrich ostwald concluded important studies conductivity electrolytic dissociation organic acids german scientist walther nernst portrait walther hermann nernst developed theory electromotive force voltaic cell showed characteristics current produced could used calculate free energy change chemical reaction producing current constructed equation known nernst equation related voltage cell properties fritz haber showed definite reduction


products result electrolytic processes potential cathode kept constant explained reduction nitrobenzene stages cathode became model similar reduction processes th century recent developments electrochemical society ecs founded robert andrews millikan began series experiments see oil drop experiment determine electric charge carried single electron johannes nicolaus br nsted martin lowry published essentially theory acids bases behave using electrochemical basis


arne tiselius developed first sophisticated electrophoretic apparatus years later awarded nobel prize work protein electrophoresis year later international society electrochemistry ise founded quantum electrochemistry developed revaz dogonadze pupils st century developments ten years research electrochemical optimization techniques essam elsahwi became first succeed performing situ characterization electrochemical stacks experiencing high industrial power levels using powerful technique dielectric spectroscopy principles oxidation reduction term redox


stands '' 'reduction oxidation''' refers electrochemical processes involving electron transfer molecule ion changing oxidation state reaction occur application external voltage release chemical energy oxidation reduction describe change oxidation state takes place atoms ions molecules involved electrochemical reaction formally oxidation state hypothetical charge atom would bonds atoms different elements ionic atom ion gives electron another atom ion


oxidation state increase recipient negatively charged electron oxidation state decrease example atomic sodium reacts atomic chlorine sodium donates one electron attains oxidation state chlorine accepts electron oxidation state reduced sign oxidation state positive negative actually corresponds value ion 's electronic charge attraction differently charged sodium chlorine ions reason form ionic bond loss electrons atom molecule called oxidation


gain electrons reduction easily remembered use mnemonic devices two popular '' oil rig '' oxidation loss reduction gain '' leo '' lion says '' ger '' lose electrons oxidation gain electrons reduction oxidation reduction always occur paired fashion one species oxidized another reduced cases electrons shared covalent bonds atoms large differences electronegativity electron assigned atom largest electronegativity determining oxidation state atom molecule loses electrons


known ' 'reducing agent'' ' 'reductant'' substance accepts electrons called ''oxidizing agent'' ''oxidant'' thus oxidizing agent always reduced reaction reducing agent always oxidized oxygen common oxidizing agent one despite name oxidation reaction necessarily need involve oxygen fact fire fed oxidant oxygen fluorine fires often unquenchable fluorine even stronger oxidant higher electronegativity thus accepts electrons even better


oxygen reactions involving oxygen gain oxygen implies oxidation atom molecule oxygen added oxygen reduced organic compounds butane ethanol loss hydrogen implies oxidation molecule lost hydrogen reduced follows hydrogen donates electron covalent bonds non metals takes electron along lost conversely loss oxygen gain hydrogen implies reduction balancing redox reactions electrochemical reactions water better understood


balancing redox reactions using ion electron method h sup sup oh sup sup ion h sub sub electrons compensate oxidation changes added cell 's half reactions oxidation reduction acidic medium acid medium h sup sup ions water added half reactions balance overall reaction example manganese reacts sodium bismuthate ''unbalanced reaction'' mn sup sup nabio sub sub bi sup sup ''oxidation'' h sub sub mn sup sup h sup sup e sup sup ''reduction'' e sup sup h sup sup bi sup sup h sub sub finally reaction balanced multiplying number electrons


reduction half reaction oxidation half reaction vice versa adding half reactions thus solving equation h sub sub mn sup sup h sup sup e sup sup e sup sup h sup sup bi sup sup h sub sub reaction balanced h sup sup mn sup sup nabio sub sub h sub sub bi sup sup na sup sup basic medium basic medium oh sup sup ions water added half reactions balance overall reaction example reaction potassium sodium sulfite ''unbalanced reaction''


kmno sub sub na sub sub sub sub h sub sub mno sub sub na sub sub sub sub koh ''reduction'' e sup sup h sub sub mno sub sub oh sup sup ''oxidation'' oh sup sup h sub sub e sup sup procedure followed acid medium multiplying electrons opposite half reactions solve equation thus balancing overall reaction e sup sup h sub sub mno sub sub oh sup sup oh sup sup h sub sub e sup sup equation balanced kmno sub sub na sub sub sub sub h sub sub mno sub sub


na sub sub sub sub koh neutral medium procedure used acid medium applied example balancing using electron ion method complete combustion propane ''unbalanced reaction'' c sub sub h sub sub sub sub co sub sub h sub sub ''reduction'' h sup sup sub sub e sup sup h sub sub ''oxidation'' h sub sub c sub sub h sub sub co sub sub e sup sup h sup sup acid basic medium electrons used compensate oxidation changes multiplied opposite half reactions thus solving equation h sup sup sub sub e sup sup h sub sub h sub sub


c sub sub h sub sub co sub sub e sup sup h sup sup equation balanced c sub sub h sub sub sub sub co sub sub h sub sub electrochemical cells electrochemical cell device produces electric current energy released spontaneous redox reaction caused electricity kind cell includes galvanic cell voltaic cell named luigi galvani alessandro volta scientists conducted several experiments chemical reactions electric current late th century electrochemical cells two conductive electrodes anode cathode anode defined


used work turn motor power light galvanic cell whose electrodes zinc copper submerged zinc sulfate copper sulfate respectively known daniell cell ref name w half reactions daniell cell ref name w zinc electrode anode zn zn sup sup e sup sup copper electrode cathode cu sup sup e sup sup cu modern cell stand electrochemical research electrodes attach high quality metallic wires stand attached potentiostat galvanostat pictured shot glass shaped container aerated noble gas sealed


teflon block example anode zinc metal oxidized loses electrons form zinc ions solution copper ions accept electrons copper metal electrode ions deposit copper cathode electrodeposit cell forms simple battery spontaneously generate flow electric current anode cathode external connection reaction driven reverse applying voltage resulting deposition zinc metal anode formation copper ions cathode ref


name w provide complete electric circuit must also ionic conduction path anode cathode electrolytes addition electron conduction path simplest ionic conduction path provide liquid junction avoid mixing two electrolytes liquid junction provided porous plug allows ion flow reducing electrolyte mixing minimize mixing electrolytes salt bridge used consists electrolyte saturated gel inverted u tube negatively charged electrons flow one direction around circuit


positively charged metal ions flow opposite direction electrolyte voltmeter capable measuring change electrical potential anode cathode electrochemical cell voltage also referred electromotive force emf cell diagram used trace path electrons electrochemical cell example cell diagram daniell cell zn zn sup sup cu sup sup cu first reduced form metal oxidized anode zn written separated


oxidized form vertical line represents limit phases oxidation changes double vertical lines represent saline bridge cell finally oxidized form metal reduced cathode written separated reduced form vertical line electrolyte concentration given important variable determining cell potential standard electrode potential allow prediction cell potential tabulations standard electrode potential available tabulations referenced standard hydrogen electrode standard hydrogen electrode undergoes


reaction h sup sup e sup sup h sub sub shown reduction fact act either anode cathode depending relative oxidation reduction potential electrode electrolyte combination term standard requires supply hydrogen gas bubbled electrolyte pressure atm acidic electrolyte h sup sup activity equal usually assumed h sup sup nbsp mol liter electrode connected electrode salt bridge form cell second electrode


also standard conditions measured cell potential called standard electrode potential electrode standard electrode potential zero definition polarity standard electrode potential provides information relative reduction potential electrode compared electrode positive potential respect means strongly reducing electrode forces anode example cu aqueous cuso sub sub standard electrode potential v conversely measured potential


negative electrode oxidizing zn znso sub sub standard electrode potential v ref name w wiberg pp ref standard electrode potentials usually tabulated reduction potentials however reactions reversible role particular electrode cell depends relative oxidation reduction potential electrodes oxidation potential particular electrode negative reduction potential standard cell potential determined looking standard electrode potentials electrodes sometimes called half cell potentials one smaller


potential zero thus cu cathode anode giving ''e'' sub cell sub ''e'' cu sup sup cu ''e'' h sup sup h sub sub ''e'' cu sup sup cu v changes stoichiometric coefficients balanced cell equation change ''e'' sub red sub value standard electrode potential intensive property spontaneity redox reaction operation electrochemical cells chemical energy transformed electrical energy expressed mathematically product cell 's emf electric charge transferred external circuit electrical energy ''e'' sub cell sub ''c'' sub trans sub ''e'' sub cell sub cell potential measured


volts v ''c'' sub trans sub cell current integrated time measured coulombs c ''c'' sub trans sub also determined multiplying total number electrons transferred measured moles times faraday 's constant ''f'' emf cell zero current maximum possible emf used calculate maximum possible electrical energy could obtained chemical reaction energy referred electrical work expressed following equation math w mathrm max w mathrm electrical nfe mathrm cell math work defined positive system since


free energy maximum amount work extracted system one write ref name swaddle pp ref math delta g nfe mathrm cell math positive cell potential gives negative change gibbs free energy consistent cell production electric current cathode anode external circuit current driven opposite direction imposing external potential work done cell drive electrolysis ref name spontaneous electrochemical reaction change gibbs free energy less zero used


generate electric current electrochemical cells basis batteries fuel cells example gaseous oxygen sub sub hydrogen h sub sub combined fuel cell form water energy typically combination heat electrical energy ref name conversely non spontaneous electrochemical reactions driven forward application current sufficient voltage electrolysis water gaseous oxygen hydrogen typical example relation equilibrium constant ''k'' gibbs free energy electrochemical cell expressed follows math delta g circ rt


ln k nfe circ mathrm cell math rearranging express relation standard potential equilibrium constant yields math e circ cell frac rt nf ln k math previous equation use briggsian logarithm shown math e circ cell frac mathrm v n log k math cell emf dependency changes concentration nernst equation standard potential electrochemical cell requires standard conditions ''g'' reactants reactant concentrations differ standard conditions cell potential deviate standard potential th century german chemist walther nernst proposed mathematical model determine effect reactant concentration electrochemical cell potential


reactant concentration spontaneity based gibbs' work nernst extended theory include contribution electric potential charged species shown previous section change gibbs free energy electrochemical cell related cell potential thus gibbs' theory becomes math nf delta e nf delta e circ rt ln q math ''n'' number electrons mole product ''f'' faraday constant coulombs mole ''e'' cell potential finally nernst divided amount charge transferred arrive new equation bears name math delta


e delta e circ frac rt nf ln q math assuming standard conditions ''t'' nbsp c r j k mol equation expressed base logarithm shown ref name w wiberg pp ref math delta e delta e circ frac mathrm v n log q math note '''' also known thermal voltage ''v'' sub sub found study plasma 's semiconductors well value nbsp v equation thermal voltage standard temperature multiplied natural logarithm concentration cells concentration cell electrochemical cell


two electrodes material electrolytes two half cells involve ions electrolyte concentration differs two half cells example electrochemical cell two copper electrodes submerged two copper ii sulfate solutions whose concentrations connected salt bridge type cell generate potential predicted nernst equation undergo chemistry although reaction proceeds reverse anode cu sup sup e sup sup cu le chatelier 's principle indicates reaction


favorable reduction concentration cu sup sup ions increases reduction take place cell 's compartment concentration higher oxidation occur dilute side following cell diagram describes cell mentioned cu cu sup sup cu sup sup cu half cell reactions oxidation reduction oxidation cu cu sup sup e sup sup reduction cu sup sup e sup sup cu overall reaction cu sup sup cu sup sup cell 's emf calculated nernst equation


follows math e e circ frac mathrm v log frac mathrm cu mathrm diluted mathrm cu mathrm concentrated math value ''e'' kind cell zero electrodes ions half cells replacing values case mentioned possible calculate cell 's potential math e frac mathrm v log frac mathrm v math math e frac mathrm v ln frac mathrm v math however value approximate reaction quotient defined terms ion activities approximated concentrations calculated nernst equation plays important


role understanding electrical effects cells organelles effects include nerve synapses cardiac beat well resting potential somatic cell battery many types battery commercialized represent important practical application electrochemistry early wet cells powered first telegraph telephone systems source current electroplating zinc manganese dioxide dry cell first portable non spillable battery type made flashlights portable devices practical mercury battery using zinc mercuric oxide provided higher levels power capacity original


dry cell early electronic devices phased common use due danger mercury pollution discarded cells lead acid battery first practical secondary rechargeable battery could capacity replenished external source electrochemical reaction produced current useful degree reversible allowing electrical energy chemical energy interchanged needed common lead acid batteries contain mixture sulfuric acid water well lead plates common mixture used today acid one problem however left uncharged


acid crystallize within lead plates battery rendering useless batteries last average years daily use however unheard lead acid battery still functional years lead acid cells continue widely used automobiles preceding types water based electrolytes limits maximum voltage per cell freezing water limits low temperature performance lithium battery cannot use water electrolyte provides improved performance types rechargeable lithium ion battery essential part


many mobile devices flow battery experimental type offers option vastly larger energy capacity reactants replenished external reservoirs fuel cell turn chemical energy bound hydrocarbon gases hydrogen directly electrical energy much higher efficiency combustion process devices powered many spacecraft applied grid energy storage public power system corrosion corrosion electrochemical process reveals rust tarnish metals like iron copper respective alloys steel brass iron


rust concentration water associated iron oxide varies thus chemical formula represented fe sub sub sub sub h sub sub electric circuit formed passage electrons ions occurs thus electrolyte present facilitate oxidation explaining rusting quicker salt water corrosion common metals coinage metals copper silver slowly corrode use patina green blue copper carbonate forms surface copper exposure water carbon dioxide air silver coins cutlery exposed high sulfur foods


eggs low levels sulfur species air develop layer black silver sulfide gold platinum extremely difficult oxidize normal circumstances require exposure powerful chemical oxidizing agent aqua regia common metals oxidize extremely rapidly air titanium aluminium oxidize instantaneously contact oxygen air metals form extremely thin layer oxidized metal surface bonds underlying metal thin layer oxide protects underlying layers metal air preventing entire


metal oxidizing metals used applications corrosion resistance important iron contrast oxide forms air water called rust bond iron therefore stop oxidation iron thus iron left exposed air water continue rust iron oxidized prevention corrosion attempts save metal becoming anodic two general types anodic regions dissolve destroy structural integrity metal almost impossible prevent anode cathode


metal cathodic thus spared corrosion called '' sacrificial '' anode dissolves replaced periodically zinc bars attached various locations steel ship hulls render ship hull cathodic zinc bars replaced periodically metals magnesium would work well zinc least expensive useful metal protect pipelines ingot buried exposed magnesium zinc buried beside pipeline connected electrically pipe ground pipeline forced cathode protected


cell cell connected electrical power supply allowing electrons migrate power supply electrolytic cell ref name e ebbing pp ref reactions take place 's cell following ref name e anode oxidation cl sup sup cl sub sub e sup sup cathode reduction na sup sup e sup sup na overall reaction na sup sup cl sup sup na cl sub sub process yield large amounts metallic sodium gaseous chlorine widely used mineral dressing metallurgy industries emf process approximately nbsp v indicating


non spontaneous process order reaction occur power supply provide least potential nbsp v however larger voltages must used reaction occur high rate electrolysis water water converted component elemental gasses h sub sub sub sub application external voltage water n't decompose hydrogen oxygen spontaneously gibbs free energy process standard conditions kj decomposition water hydrogen oxygen performed electrolytic cell pair


inert electrodes usually made platinum immersed water act anode cathode electrolytic process electrolysis starts application external voltage electrodes process occur except extremely high voltages without electrolyte sodium chloride sulfuric acid used ref name w bubbles gases seen near electrodes following half reactions describe process mentioned anode oxidation h sub sub sub sub h sup sup e sup sup cathode reduction h sub sub e sup sup h sub sub oh sup sup overall


reaction h sub sub h sub sub sub sub although strong acids may used apparatus reaction net consume acid reaction work conductive electrode sufficiently large potential platinum catalyzes hydrogen oxygen formation allowing relatively mild voltages v depending ph ref name w wiberg pp ref electrolysis aqueous solutions electrolysis aqueous solution similar process mentioned electrolysis water however considered complex process contents solution analyzed half reactions


whether reduced oxidized electrolysis solution sodium chloride presence water solution sodium chloride must examined respect reduction oxidation electrodes usually water electrolysed mentioned electrolysis water yielding ''gaseous oxygen anode'' gaseous hydrogen cathode hand sodium chloride water dissociates na sup sup cl sup sup ions cation positive ion attracted cathode thus reducing sodium ion anion attracted anode oxidizing chloride


ion ref name nacl ebbing pp ref following half reactions describes process mentioned ref name nacl cathode na sup sup e sup sup na''e'' sub red sub v anode cl sup sup cl sub sub e sup sup ''e'' sub red sub v cathode h sub sub e sup sup h sub sub oh sup sup ''e'' sub red sub v anode h sub sub sub sub h sup sup e sup sup ''e'' sub red sub v reaction discarded negative value standard reduction potential thus making less thermodynamically favorable process comparing reduction potentials reactions


oh sup sup overall reaction h sub sub cl sup sup h sub sub cl sub sub oh sup sup overall reaction indicates concentration chloride ions reduced comparison oh sup sup ions whose concentration increases reaction also shows production gaseous hydrogen chlorine aqueous sodium hydroxide quantitative electrolysis faraday 's laws quantitative aspects electrolysis originally developed michael faraday faraday also credited coined terms ''electrolyte'' electrolysis among many others studied quantitative analysis electrochemical reactions also advocate law conservation energy


first law faraday concluded several experiments electric current non spontaneous process mass products yielded electrodes proportional value current supplied cell length time current existed molar mass substance analyzed words amount substance deposited electrode electrolytic cell directly proportional quantity electricity passed cell simplified equation faraday 's first law math frac mathrm c cdot mol cdot frac qm n math ''m'' mass


different elements deposited given amount electricity ratio chemical equivalent weights important aspect second law electrolysis electroplating together first law electrolysis significant number applications industry used protect metals avoid corrosion applications various extremely important electrochemical processes nature industry like coating objects metals metal oxides electrodeposition addition electroplating removal electropolishing thin layers metal object 's surface detection