Electrical Terms Z A ACTUATOR SOLENOID - The solenoid in the actuator housing on the back of the injection pump which moves the control rack as commanded by the engine controller. ALTERNATOR - A device which converts mechanical energy into electrical energy. ALTERNATING CURRENT (AC) - A flow of electrons which reverses its direction of flow at regular intervals in a conductor. AMBIENT TEMPERATURE - The temperature of the surrounding medium, such as gas, air or liquid, which comes into contact with a particular component. AMMETER - An instrument for measuring the flow of electrical current in amperes. Ammeters are always connected in series with the circuit to be tested. AMPERE - A unit of measure for the flow of current in a circuit. One ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance. The ampere is used to measure electricity much as "gallons per minute" is used to measure water flow. AMPERE-HOUR - A unit of measure for battery capacity. It is obtained by multiplying the current (in amperes) by the time (in hours) during which current flows.

For example, a battery which provides 5 amperes for 20 hours is said to deliver 100 ampere - hours. AMPLIFIER - A device of electronic components used to increase power, voltage, or current of a signal. AMPLITUDE - A term used to describe the maximum value of a pulse or wave. It is the crest value measured from zero. ANALOG IC - lntegrated circuits composed to produce, amplify, or respond to variable voltages. They include many kinds of amplifiers that involve analog - to - digital conversions and vice versa, timers, and inverters. They are known as Operational Amplifier Circuits or OP - Amps. ANALOG GAUGE - A display device utilizing a varying current to cause a mechanical change in the position of its needle. ARMATURE - The movable part of a generator or motor. It is made up of conductors which rotate through a magnetic field to provide voltage or force by electromagnetic induction. The pivoted points in generator regulators are also called armatures. ARTIFICIAL MAGNETS - A magnet which has been magnetized by artificial means. It is also called, according to shape, a bar magnet or a horseshoe magnet.

ATOM - A particle which is the smallest unit of a chemical element. It is made up mainly of electrons (minus charges) in orbit around protons (positive charges). AUXiliARY SPEED SENSOR - The engine speed sensor located on the engine timing gear cover. It serves as a back - up to the primary engine speed sensor. Back to Top B BENDIX DRIVE - One type flywheel engaging device for a starting motor. It is said to be mechanical because it engages by inertia. BREAK - See " Open ." BRUSH - A device which rubs against a rotating slip ring or commutator to provide a passage for electric current to a stationary conductor. CALIBRATION - The determination or rectification of the graduations used on a testing instrument. CAPACITOR - A device which stores electrical energy. Commonly used for filtering out voltage spikes. CHARGE - To restore the active materials in a storage battery by the passage of direct current through the battery cells in a direction opposite that of the discharging current. CURRENT - Movement of electricity along a conductor. Current is measured in amperes. CURRENT FLOW - The flow or movement of electrons from atom to atom in a conductor.

CYCLE - The change in an alternating electrical sine wave from zero to a positive peak to zero to a negative peak and back to zero. CYCLING - The process by which a battery is discharged and recharged. Back to Top D DIAGNOSTIC CODE - A number which represents a problem detected by the engine controller. Diagnostic codes are transmitted for use by on - board displays or a diagnostic reader so the operator or technician is aware there is a problem and in what part of the fuel injection system the problem can be found. DIFFERENTIATOR CIRCUIT - A circuit that consists of resistors and capacitors designed to change a DC input to an AC output. It is used to make narrow pulse generators and to trigger digital logic circuits. When used in integrated circuits it is known as an inverter. DIGITAL IC - lntegrated circuits that produce logic voltage signals or pulses that have only two levels of output that are either ON or OFF (yes or no). Some component output examples are: Diagnostic Codes Output, Pulse - Width - Modulated (PWM) Throttle Output, Auxiliary Speed Output, and Fuel FlowfThrottle Output. DIODE - An electrical device that will allow current to pass through itself in one direction only.

Also see " Zener diode ." DIRECT CURRENT (DC) - A steady flow of electrons moving steadily and continually in the same direction along a conductor from a point of high potential to one of lower potential. It is produced by a battery, generator, or rectifier. DISCHARGE - To remove electrical energy from a charged body such as a capacitor or battery. DISTRIBUTOR (IGNITION) - A device which directs the high voltage of the ignition coil to the engine spark plugs. DISTRIBUTOR LEAD CONNECTOR - A connection plug in the wires that lead from the sensor in the distributor to the electronic control unit. DYER DRIVE - One type of flywheel engaging mechanism in a starting motor. ELECTRICAL FIELD - The region around a charged body in which the charge has an effect. ELECTRICITY - The flow of electrons from atom to atom in a conductor. ELECTROCHEMICAL - The relationship of electricity to chemical changes and with the conversions of chemical and electrical energy. A battery is an electrochemical device. ELECTRO-HYDRAULIC VALVE - A hydraulic valve actuated by a solenoid through variable voltage applied to the solenoid coil.

ELECTROLYTE - Any substance which, in solution, is dissociated into ions and is thus made capable of conducting an electrical current. The sulfuric acid - water solution in a storage battery is an electrolyte. ELECTROMAGNET - core of magnetic material, generally soft iron, surrounded by a coil of wire through which electrical current is passed to magnetize the core. ELECTROMAGNETIC CLUTCH - An electromagnetic device which stops the operation of one part of a machine while other parts of the unit keep on operating. ELECTROMAGNETIC FIELD - The magnetic field about a conductor created by the flow of electrical current through it. ELECTROMAGNETIC INDUCTION - The process by which voltage is induced in a conductor by varying the magnetic field so that lines of force cut across the conductor. ELECTRON - A tiny particle which rotates around the nucleus of an atom. It has a negative charge of electricity. ELECTRON THEORY - The theory which explains the nature of electricity and the exchange of "free" electrons between atoms of a conductor. It is also used as one theory to explain direction of current flow in a circuit.

ELECTRONICS - The control of electrons (electricity) and the study of their behavior and effects. This control is accomplished by devices that resist, carry, select, steer, switch, store, manipulate, and exploit the electron. ELECTRONIC CONTROL UNIT (ECU) - General term for any electronic controller. See "controller:' ELECTRONIC GOVERNOR - The computer program within the engine controller which deterines the commanded fuel delivery based on throttle command, engine speed, and fuel temperature. It replaces the function of a mechanical govnor. ELECTRONIC IGNITION SYSTEM - A system in which the timing of the ignition spark is controlled electronically. Electronic ignition systems have no points or condenser, but instead have a reluctor, sensor, and electronic control unit. ELEMENT - (1) Any substance that normally cannot be separated into different substances. (2) The completed assembly of a battery consisting of negative plates, positive plates, and separators mounted in a cell compartment. ENGINE CONTROLLER - The electronic module which controls fuel delivery, diagnostic outputs, back - up operation, and communications with other electronic modules. Back to Top F FIELD EFFECT TRANSISTOR (FET) - A transistor which uses voltage to control the flow of current.

Connections are the source (input), drain (output) and gate (control). FIXED RESISTOR - A resistor which has only one resistance value. FREOUENCY - The number of pulse or wave cycles that are completed in one second. Frequency is measured in Hertz, as in 60Hz (hertz) per second. FUNDAMENTAL LAW OF MAGNETISM - The fundamental law of magnetism is that unlike poles attract each other, and like poles repel each other. FUSE - A replaceable safety device for an electrical circuit. A fuse consists of a fine wire or a thin metal strip encased in glass or some fireresistant material. When an overload occurs in the circuit, the wire or metal strip melts, breaking the circuit. Back to Top G GATE - A logic circuit device which makes a YES or NO (one or zero) decision (output) based on two or more inputs. GENERATOR - A device which converts mechanical energy into electrical energy. GRID - A wire mesh to which the active materials of a storage battery are attached. GROUND - A ground occurs when any part of a wiring circuit unintentionally touches a metallic part of the machine frame.

GROUNDED CIRCUIT - A connection of any electrical unit to the frame, engine, or any part of the tractor or machine, completing the electrical circuit to its source. GROWLER - A device for testing the armature of a generator or motor. Back to Top H HYDROMETER - An instrument for measuring specific gravity. A hydrometer is used to test the specific gravity of the electrolyte in a battery. I IGNITION CONTROL UN IT - The module that contains the transistors and resistors that controls the electronic ignition. INDUCTANCE - The property of an electric circuit by which an electromotive force (voltage) is induced in it by a variation of current either in the circuit itself or in a neighboring circuit. INDUCTOR - A coil of wire wrapped around an iron core. INSULATED GATE FIELD EFFECT TRANSISTOR (IGFET) - A diffused transistor which has an insulated gate and almost infinite gate - channel resistance. INSULATOR - A substance or body that resists the flow of electrical current through it.

Also see "Conductor:' INTEGRATED CIRCUIT (IC) - An electronic circuit which utilizes resistors, capacitors, diodes, and transistors to perform various types of operations. The two major types are Analog and Digital Integrated Circuits. Also see " Analog IC " and " DigitaI IC ." INTEGRATOR CIRCUIT - A circuit that consists of resistors and capacitors and functions as a filter which can pass signals only below a certain frequency. INVERTER - A device with only one input and one output; it inverts or reverses any input. ION - An atom having either a shortage or excess of electrons. ISOLATION DIODE - A diode placed between the battery and the alternator. It blocks any current flow from the battery back through the alternator regulator when the alternator is not operating. Back to Top L LIGHT EMITTING DIODE (LED) - A solid - state display device that emits infrared light when a forward - biased current flows through it. LINES OF FORCE - Invisible lines which conveniently illustrate the characteristics of a magnetic field and magnetic flux about a magnet.

LIQUID CRYSTAL DISPLAY (LCD) - A display device utilizing a special crystal fluid to allow segmented displays. Back to Top M MAGNET - A body which has the property of at. tracting iron or other magnets. Its molecules are aligned. MAGNETIC FIELD - That area near a magnet in which its property of magnetism can be detected. It is shown by magnetic lines of force. MAGNETIC FLUX - The flow of magnetism about a magnet exhibited by magnetic lines of force in a magnetic field. MAGNETIC INDUCTION - The process of introducing magnetism into a bar of iron or other magnetic material. MAGNETIC LINES OF FORCE - Invisible lines which conveniently illustrate the characteristics of a magnetic field and magnetic flux about a magnet. MAGNETIC MATERIAL - Any material to whose molecules the property of magnetism can be imparted. MAGNETIC NORTH - The direction sought by the north pole end of a magnet, such as a magnetic needle, in a horizontal position. It is near the geographic north pole of the Earth.

MAGNETIC PICKUP ASSEMBLY - The assembly in a self - integrated electronic ignition system that contains a permanent magnet, a pole piece with internal teeth, and a pickup coil. These parts, when properly aligned, cause the primary circuit to switch off and induce high voltage in the secondary windings. MAGNETIC SOUTH - The opposite direction from magnetic north towards which the south pole end of a magnet, such as a magnetic needle, is attracted when in a horizontal position. It is near the geographic south pole of the Earth. MAGNETIC SWITCH - A solenoid which performs a simple function, such as closing or opening switch contacts. MAGNETISM - The property inherent in the molecules of certain substances, such as iron, to become magnetized, thus making the substance into a magnet MICROPROCESSOR - An integrated circuit combing logic, amplification and memory functions. MILLIAMPERE - 1/1,OOO,OOO ampere. MOLECULE - A unit of matter which is the smallest portion of an element or compound that retains chemical identity with the substance in mass. It is made up of one or more atoms. MOTOR - A device which converts electric energy into mechanical energy.

MUL TIMETER - A testing device that can be set to read ohms (resistance), voltage (force), or amperes (current) of a circuit. MUTUAL INDUCTION - Occurs when changing current in one coil induces voltage in a second coil. Back to Top N NATURAL MAGNET - A magnet which occurs in nature, such as a lodestone. Its property of magnetism has been imparted by the magnetic effects of the Earth. NEGATIVE - Designating or pertaining to a kind of electricity. Specifically, an atom that gains negative electrons is negatively charged. NEUTRON - An uncharged elementary particle. Present in all atomic nuclei except the hydrogen nucleus. NON-MAGNETIC MATERIAL - A material whose molecules cannot be magnetized. NORMALLY OPEN and NORMALLY CLOSED - These terms refer to the position taken by the contacts in a magnetically operated switching device, such as a relay, when the operating magnet is de. energized. 0 OHM - The standard unit for measuring resistance to flow of an electrical current. Every electrical conductor offers resistance to the flow of current, just as a tube through which water flows offers resistance to the current of water.

One ohm is the amount of resistance that limits current flow to one ampere in a circuit with one volt of electrical pressure. OHMMETER - An instrument for measuring the resistance in ohms of an electrical circuit. OHM'S LAW - Ohm's Law states that when an electric current is flowing through a conductor, such as a wire, the intensity of the current (in amperes) equals the electromotive force (volts) driving it, divided by the resistance of the conductor. The flow is in proportion to the electromotive force, or voltage, as long as the resistance remains the same. OPEN OR OPEN CIRCUIT - An open or open circuit occurs when a circuit is broken, such as by a broken wire or open switch, interrupting the flow of current through the circuit. It is analogous to a closed valve in a water system. OPERATIONAL AMPLIFIER - A high - voltage gain, low - power, linear amplifying circuit device used to add, subtract, average, etc. OVERRUNNING CLUTCH - One type of flywheelengaging member in a starting motor.

Back to Top P PARALLEL CIRCUIT - A circuit in which the circuit components are arranged in branches so that there is a separate path to each unit along which electrical current can flow. PERMANENT MAGNET - A magnet which retains its property of magnetism for an indefinite period. PIEZO ELECTRIC DEVICE - A device made of crystalline materials, such as quartz, which bend or distort when force or pressure is exerted on them. This pressure forces the electrons to move. PLATE - A solid substance from which electrons flow. Batteries have positive plates and negative plates. POLARITY - A collective term applied to the positive (+) and negative ( - ) ends of a magnet or electrical mechanism such as a coil or battery. POLE - One or two points of a magnet at which its magnetic attraction is concentrated. POLE SHOES - Iron blocks fastened to the inside of a generator or motor housing around which the field or stator coils are wound. The pole shoes may be permanent or electro - magnets. POSITIVE - Designating or pertaining to a kind of electricity. Specifically, an atom which loses negative electrons and is positively charged. POTENTIOMETER - A variable resistor used as a voltage divider.

POWER SWITCH TRANSISTOR - The part responsible for switching off the primary circuit that causes high voltage induction in the secondary winding in an electronic ignition system. PRIMARY SPEED SENSOR - An engine speed sensor located inside the actuator housing on the back of the injection pump. PRINCIPLE OF TURNING FORCE - Explains how magnetic force acts on a current - carrying conductor to create movement of an armature, such as in an electric motor. PRINTED CIRCUIT BOARD - A device used to hold integrated circuit components in place and provide current paths from component to component. Copper pathways are etched into the board with acid. PROTON - A particle which, together with the neutron constitutes the nucleus of an atom. It exhibits a positive charge of electricity. PULSE - A signal that is produced by a sudden ON and OFF of direct current (DC) within a circuit. PULSE-WIDTH-MODULATED (PWM) - A digital electronic signal which consists of a pulse generated at a fixed frequency. The information transmitted by the signal is contained in the width of the pulse. The width of the pulse is changed (modulated) to indicate a corresponding change in the information being transmitted, such as throttle command.

Back to Top R RECTIFIER - A device (such as a vacuum tube, commutator, or diode) that converts alternating current into direct current. REGULATOR - A device which controls the flow of current or voltage in a circuit to a certain desired level. RELAY - An electrical coil switch that uses a small current to control a much larger current. RELUCTANCE - The resistance that a magnetic circuit offers to lines of force in a magnetic field. RELUCTOR - A metal cylinder, with teeth or legs, mounted on the distributor shaft in an electronic ignition system. The reluctor rotates with the distributor shaft and passes through the electromagnetic field of the sensor. RESISTANCE - The opposing or retarding force offered by a circuit or component of a circuit to the passage of electrical current through it. Resistance is measured in ohms. RESISTOR - A device usually made of wire or carbon which presents a resistance to current flow. RHEOSTAT - A resistor used for regulating a current by means of variable resistance; rheostats allow only one current path. RIGHT-HAND RULE - A method used to determine the direction a magnetic field rotates about a conductor, or to find the north pole of a magnetic field in a coil.

ROTOR - The rotating part of an electrical machine such as a generator, motor, or alternator. S SELF-INDUCTION - Voltage which occurs in a coil when there is a change of current. SEMICONDUCTOR - An element which has four electrons in the outer ring of its atoms. Silicon and germanium are examples. These elements are neither good conductors nor good insulators. Semiconductors are used to make diodes, transistors, and integrated circuits. SENDING UNIT - A device, usually located in some part of an engine, to transmit information to a gauge on an instrument panel. SENSOR - A small coil of fine wire in the distributor on electronic ignition systems. The sensor develops an electromagnetic field that is sensitive to the presence of metal. In monitors and controllers, they sense operations of machines and relay the information to a console. SEPARATOR - Any of several substances used to keep one substance from another. In batteries a separator separates the positive plates from the negative plates. SERIES CIRCUIT - A circuit in which the parts are connected end to end, positive pole to negative pole, so that only one path is provided for current flow.

SERIES-PARALLEL CIRCUIT - A circuit in which some of the circuit components are connected in series and others are connected in parallel. SHORT (OR SHORT CIRCUIT) - This occurs when one part of a circuit comes in contact with another part of the same circuit, diverting the flow of current from its desired path. SHUNT - A conductor joining two points in a circuit so as to form a parallel circuit through which a portion of the current may pass. SLIP RING - In a generator, motor, or alternator, one of two or more continuous conducting rings from which brushes take, or deliver to, current. SOLENOID - A tubular coil used for producing a magnetic field. A solenoid usually performs some type of mechanical work. SOLID-STATE CIRCUITS - Electronic (integrated) circuits which utilize semiconductor devices such as transistors, diodes and silicon controlled rectifiers. SPARK PLUGS - Devices which ignite the fuel by a spark in a spark - ignition engine. SPECIFIC GRAVITY - The ratio of a weight of any volume of a substance to the weight of an equal volume of some substance taken as a standard, usually water for solids and liquids.

When a battery electrolyte is tested the result is the specific gravity of the electrolyte. SPRAG CLUTCH DRIVE - A type of flywheel engaging device for a starting motor. STARTER MOTOR - A device that converts electrical energy from the battery into mechanical energy that turns an engine over for starting. STATOR - The stationary part of an alternator in which another part (the rotor) revolves. STORAGE BATTERY - A group of electrochemical cells connected together to generate electrical energy. It stores the energy in a chemical form. SULFATION - The formation of hard crystals of lead sulfate on battery plates. The battery is then "sulfated." SWITCH - A device which opens or closes electrical pathways in an electrical circuit. SYNCHROGRAPH - An all - purpose distributor tester. T TACHOMETER - An instrument for measuring rotary speed; usually revolutions per minute. TEMPORARY MAGNET - A magnet which loses its property of magnetism quickly unless forces act to re - magnetize it. THERMISTOR - A temperature - compensated resistor. The degree of its resistance varies with the temperature. In some regulators, it controls a Zener diode so that a higher system voltage is produced in cold weather, when needed.

TRANSFORMER - A device made of two coil windings that transfers voltage from one coil to the next through electromagnetic induction. Depending upon the number of windings per coil, a transformer can be designed to step - up or step - down its output voltage from its input voltage. Transformers can only function with alternating current (AC). TRANSIENT VOLTAGE PROTECTION MODULE (TVP) - A device which protects the engine controller electronics against high energy voltage transients such as alternator load dumps. TRANSISTOR - A device constructed of semi - conductors that is used in circuits to control a larger current by using a smaller current for operation. Its function is the same as a relay. TRIMMER RESISTOR - A resistor used in applications where only a small resistance change is needed. Back to Top V VACUUM FLORESCENT DISPLAY (VDC) - An anode - controlled display which emits its own light. It works like a television tube, directing streams of electrons to strike phosphorescent segments. VARIABLE RESISTOR - A resistor that can beadjusted to different ranges of value. VISCOSITY - The internal resistance of a fluid, caused by molecular attraction, which makes it resist a tendency to flow.

VOLT - A unit of electrical pressure (or electromotive force) which causes current to flow in a circuit. One volt is the amount of pressure required to cause one ampere of current to flow against one ohm of resistance. VOLTAGE - That force which is generated to cause current to flow in an electrical circuit. It is also referred to as electromotive force or electrical potential. Voltage is measured in volts. VOLTAGE REGULATOR - A device that controls the strength of a magnetic field produced by a generator or alternator. It prevents the battery from being overor undercharged during high - or low - speed operation of the generator or alternator. VOLTMETER - An instrument for measuring the force in volts of an electrical current. This is the difference of potential (voltage) between different points in an electrical circuit. Voltmeters are connected across (parallel to) the points where voltage is to be measured. Back to Top W WATT - A unit of measure for indicating the electrical power applied in a circuit. It is obtained by multiplying the current (in amperes) by the electrical pressure (in volts) which cause it to flow. That is: watts = amperes x volts.

WATT-HOUR - A unit of electrical energy. It indicates the amount of work done in an hour by a circuit at a steady rate of one watt. That is, watthours = ampere - hours x volts. WAVE - A signal that is produced by varying a continuous flow of current within a circuit. Waveforms can be created by either AC or DC current. WAVEFORM - A graphical representation ofelectrical cycles which shows the amount of variation in amplitude over some period of time. WINDING - The coiling of a wire about itself or about some object. Often identified as a series winding, a shunt winding, etc. WIRING HARNESS - Thf3 trunk and branches which feed an electrical circuit. Wires from one part of the circuit enter the trunk, joining other wires, and then emerge at another point in the circuit. Back to Top Z ZENER DIODE (Reverse Bias Direction Diode) - A semiconductor device that will conduct current in the reverse direction when the voltage becomes higher than a predetermined voltage. Glossary Order the DVD/Video For related links use the NavKnob® above to search the site for the word in question.

It will provide you with a list of links to pages within the site where the term is mentioned or discussed. Glossary Alternating Current (AC): A type of electrical current in which the direction of the flow of electrons switches back and forth. In the US, the current that comes from a wall outlet is alternating; it cycles back and forth sixty times each second. The current that flows in a flashlight, on the other hand, is direct current (DC), which does not alternate. Amplifier: A device which takes in a weak electric signal and sends out a stronger one. Amplifiers are used to boost electrical signals in many electronic devices, including radios, televisions, and telephones. Both vacuum tubes and transistors can be amplifiers, though today vacuum tubes are rarely used for this purpose. Atoms: The smallest possible piece of any pure element that still has the properties of that element. Atoms are made of smaller particles including electrons, protons, and neutrons. Differences in the numbers of these particles create the differences between the elements. An atom is about 500-billionths of an inch, or a hundred millionths of a centimeter across.

Audion: A special kind of vacuum tube which can be used to amplify weak electric signals. The audion was used in the Bell phone system, as well as in early radios and computers. It was eventually replaced in most applications by the transistor. Capacitor: A device that stores electrical charge, using a positively charged surface and a negatively charged surface with a gap between them. The Leyden jar, used by early electrical experimenters (including Benjamin Franklin) was a form of capacitor. A smaller kind of capacitor is often used in electrical circuits. Cat's Whisker: A tiny metal wire used in early home radio kits. Radio listeners carefully moved the wire tips around on the surface of a crystal to just the right spot to allow an electrical signal to travel down one wire, through the crystal and out the other wire. If the wires were positioned on the right spot, and it was often tough to find the right spot, the radio signal could be heard through the earphones. Charge: An electrical property of particles, such as electrons and protons, which causes them to attract and repel each other.

A material with an excess of electrons is defined to have a "negative" charge; material with an absence of electrons (or an excess of protons) is defined as "positive." Materials with a balanced number of electrons and protons are called "neutral." Positive and negative charges attract each other. That attraction can cause interesting effects at the junction between positive and negative semiconductors. This special junction is what makes the right configuration of semiconductors work as a transistor. Circuit: A string of electronic devices such as transistors, resistors, capacitors, and diodes connected by wires so that current can run through it in a complete loop. Circuits can be simple or complex. The wiring connecting a switch to a light to the power source and back to the switch is a simple circuit; opening the switch breaks the circuit and stops the current flow. Even a computer chip is simply an extremely complicated network of circuits. Conductor: Any material that easily allows the flow of electricity. Metals are good conductors. Such materials conduct electricity because electrons can move from one atom of a conductor to the next, forming an electric current.

Crystal: A chunk of solid material in which all the atoms are lined up in an orderly pattern like rows of oranges in a grocery store. Transistors are made out of semiconductor crystals. Growing perfect germanium and silicon crystals with no defects or unwanted impurities is key to building a working transistor. Current: The flow of charge carriers (holes or electrons) through a conducting wire or crystal. Diode: Rectifier. An electronic device with two wires or terminals. A rectifier allows electrical current to flow through in only one direction and is used for converting alternating current into direct current. Rectifiers were important for use in radios, which required direct current to power the amplifiers driving speakers or headphones. Direct Current (DC): Current which moves in a single direction in a steady flow. Normal household electricity is alternating current (AC) which repeatedly reverses its direction. However, many electronics devices require DC, and therefore must convert the current into DC before using it. Diodes are used to convert AC to DC. Doping: Deliberately adding a very small amount of foreign substance to an otherwise very pure semiconductor crystal.

These added impurities give the semiconductor an excess of conducting electrons or an excess of conducting holes (the absence of conducting electrons) which is crucial for making a working transistor. Electric Field: The region around any electrically charged material contains an electric field that affects other charged objects. The field around a negatively charged material pulls positively-charged objects in toward the material, while negatively-charged objects are pushed away. Around a positively charged material, on the contrary, negative objects are attracted and positive objects are repelled. The strength of the field gets rapidly weaker as one moves further away from the charged material. Electric Signal: Information expressed through changes in an electric current. Information can be encoded in on-and-off switches of current, in the amplitude of the current, or in other easily-detectable changes. Sound waves, for example, can be converted to electricity by a microphone and sent as an electrical signal through the wires of a stereo to the speakers. Electrode: An electrical lead or wire attached to any electronic device or circuit through which current may flow in or out. Electron: Electrons are one of the particles that makes up an atom and particles that, in motion, can form an electric current.

An electron is 2000 times lighter than the lightest atom. Element: Any of over a hundred fundamental materials containing only one kind of atom. Some common elements are oxygen, gold, hydrogen, and silicon. All other materials are made of compounds or mixtures of elements. Water, for example, is made of two hydrogen atoms attached to one oxygen atom. Field-effect transistor: The most common type of modern transistor, and the type of transistor used in integrated circuits. The field-effect transistor is so named because an incoming weak electrical signal creates an electrical field across a section of semiconductor. This field causes a second electrical current to flow across the semiconductor, identical to the first weak signal, but stronger. Four-layer diode: A semiconductor device which can take alternating current and turn it into direct current but which also stops letting any current through once a certain voltage is reached. The diode is made of four layers of alternating types of semiconductor. Germanium: A chemical element that acts as a semiconductor, meaning sometimes it conducts electricity and sometimes it doesn't. The first transistors were all made out of germanium.

Holes: When an array of atoms in a crystal is missing a conducting electron, it's said to have a "hole." Since conducting electrons are negative, holes are positive. Even though holes are an absence of a conducting electron, scientists often talk about holes flowing as if they were real particles. Insulator: Any material that does not conduct electricity. Glass and rubber are common insulators. These materials are made of atoms which don't allow electrons to move freely, which means there can be no electric current. Integrated Circuit: A collection of transistors and electrical circuits all built onto a single crystal. Today's integrated circuits are no more than a centimeter long, and they can carry millions of microscopic transistors. All computers have integrated circuits inside. Junction Transistor: The second type of transistor built, and a direct ancestor of modern day transistors. It consists of two sections of one type of semiconductor (N- or P-) around a middle slab of the other type. The junctions between the semiconductor sections cause an incoming weak electrical signal to be amplified. Microprocessor: A circuit of transistors and other electrical components on a chip that can process programs, remember information, or perform calculations.

N-type semiconductor: A semiconductor which has an excess of conduction electrons. A semiconductor can be made into N-type by adding trace amounts of another element to the original semiconductor crystal. Today's transistors all require sections of both N-type and P-type semiconductors. P-type semiconductor: A semiconductor which has an excess of conducting holes. It is created by adding trace amounts of other elements to the original pure semiconductor crystal. Today's transistors all require sections of both N- type and P-type semiconductors. Point-contact transistor: The very first type of transistor ever made, invented by John Bardeen and William Brattain. So-called because it consists of two metal points making light contact with the surface of a germanium crystal. Rectifier: See Diode Semiconductor: A material that conducts more than an insulator but less than a conductor. Some semiconductors conduct at some times but not at others. Some common semiconductors are silicon and germanium. Transistors are made out of semiconductor crystals. Silicon: Silicon is one of the most common elements on Earth in the Earth's crust, it's second in mass only to oxygen and can be found in any quartz crystal. Beach sand is largely silicon.

Silicon is also the semiconductor material out of which almost all modern transistors are made. Solid State: Relating to the properties of solid, usually crystalline, materials including semiconductors. Solid state science is often a mixture of physics, and chemistry, and materials science. Transistor: Transistors are tiny electrical devices that can be found in everything from radios to robots. They have two key properties: 1) they can amplify an electrical signal and 2) they can switch on and off, letting current through or blocking it as necessary. Type-A transistor: What Bell called the first point-contact transistors they built. These were installed into the Bell Phone system, and given to the military and scientists for other purposes as well -­ but the Type-A transistor was never widely used. Voltage: Voltage is a measure of the energy required to move a charge from one point to another. A difference in the amount of electric charge between two points creates a difference in potential energy, measured in "volts," which causes electrons to flow from an area with more electrons to an area with fewer, producing an electric current. Semiconductors: Thyristors and More 1.) Basics What is a Semiconductor?

Semiconductor materials are materials with that allow electricity to pass through due to electron flow. In contrast, normal conductors have ionic conductivity. Various elements are semiconductors. One of the first to be experimented with was germanium (Ge) (Element # 32). Silicon and Gallium are more well known semiconductors today. Semiconductors are so universal in application due to the ability of humans to precisely control how these materials conduct electricity: by controlling crystal size of the element and doping one can achieve desired resistively. Doping is introducing certain impurities into a pure sample of semiconductor to achieve desired properties. Doping a semiconductor to high levels makes the material act more like a conductor, this is called degenerate. A lightly doped semiconductor is called extrinsic. There are many methods of doping materials and it is a highly complex area of study. To understand p-n junctions and semiconductors better you will need to invest a good amount of time in a lecture, it is not a simple phenomena and far too lengthy to cover here. See a 59 minute introduction lecture to solid state (semiconductors) from ITT Madras here.

The Future: Semiconductors are the basis of consumer electronics today and will continue to be vital long into the future. Technologies which will replace many semiconductor electronics will be carbon nanotube based electronics and artificial diamonds. The military and NASA use diamonds instead of silicon wafers because they are less prone to damage by harmful rays in space. Solid state technology used in our power grid and electronics is prone to damage during solar flare events or other electromagnetic pulse events. Construction: Semiconductor devices consist of one or more p-n junctions. In the graphic below you see a simple semiconductor device consisting of a single crystal of gallium arsenide. The n region may be doped with Tellurium and the p region may be doped with zinc. There are many materials that can be used for doping. We have a video on how this works here. Important Semiconductor Devices: Learn more about triacs here > Diac - (Diode for Alternating Current). Like an SCR except that it works in both directions. It doesn't conduct until a breakover voltage is released, then it conducts until current drops below a certain threshold. When the polarity reverses it will work the same way again. There are several kinds of diacs.

The power diac is called a sidac in Japan and was first used in the first lamp dimmers sold to consumers in the US. That diac was built by Hutson of Texas. This diac dimmer was later replaced by the SCR. The other signal diode, called diac, is a low voltage device used primarily to gate SCRs and triacs but is not capable of carrying any particular power. There are other diacs formally known as quadracs (a diac-triac combination) and alternistors. Today the devices are now available up to 3000 amps and 10k volts with at least 25 different structures. Below video: basics of making integrated circuits on silicon wafers (part of our Copper in our Electrical World Series). 4.) History: Major events and dates: 1906 - First semiconductor device: ' Cat's Whisker ' detector developed - uses wire in close contact with Galena 1925 - Field-effect transistor idea developed by Julius Edgar Lilienfeld, but he could not build a working model due to substandard materials.

1934 - Oskar Heil also develops a field-effect transistor 1947 - Bardeen and Brattain discover amplification effect in germanium at Bell Labs. This is the first point-contact transistor 1948 - Point-contact Transistor also discovered independently in Germany 1949 - Werner Jacobi makes the first "integrated circuit" made of 5 transistors 1953 - First transistor sold commercially by Philco 1954 - First silicon transistor made by Texas Instruments 1955 - First all transistor car radio made by Philco Above: Bob Hall (left) and Saul Dushman look at a large single germanium crystal at General Electric. Hall's work led to great improvements in the transistor, meanwhile in the same GE labs vacuum tubes were reduced from fragile, large glass tubes to ceramic, durable pea-sized cylinders. GE Management chose to go put their wait behind the new small vacuum tubes. Bell Labs ended up winning in this battle as solid state replaced tubes. 1956 - Thyristor first commercially available 1957 - Gordon Hall and Frank W.

(Bill) Gutzwiller develop the SCR (silicon controlled rectifier) at General Electric. Gutzwiller drew the idea on paper while Hall built it and according to some deserves the credit. Gordon Hall at the Clyde facility of the Semiconductor Products Department was challenged by his manager Ray York to see if he could an SCR which had only been theorized at that point. He was successful however Bob Mooney (patent attorney) felt that defending the application would cost so much that it would not be something that the SPD could afford to do. Please note that many people helped develop this technology at Bell Labs and General Electric. Nick Holonyak and Dick Aldrich left Bell Labs and were sent to the Advanced Semiconductor Lab at GE Syracuse under the direction of Harris Sullivan. As with the MRI and other technologies there has been much controversy over who invented the device. "Bill [Gutzwiller] was manager of Application Engineering and had suggested that it would be wonderful to have a rectifier with a control electrode. But such suggestions do not constitute invention, nor reduction to practice." 1958 - Texas Instruments makes the first real "integrated circuit" consisting of one piece of semiconductor material with multiple components inside it.

1960 - First MOS - metal-oxide-semiconductor field-effect transistor 5.) Featured Pioneers: How to Convert AC to DC: 6 Steps (with Pictures) - wikiHow Community Q&A Alternating current (AC) is the most efficient way to deliver electrical power. However, most electronic devices need direct current (DC) to function. For this reason, AC to DC converters are either a part of devices themselves or as part of their power cords. If you've built a device you wish to power from an AC outlet, you must add an AC to DC converter. Steps 1 Determine what your AC input voltage is. In North America and parts of Central and South America, the AC voltage at most sockets is 110 to 120 volts at 60 hertz. In Europe, Asia, Australia and most of the Middle East and Africa, it's 230 to 240 volts at 50 hertz. The standard in other areas may differ. 2 Find the voltage and amperage needed to power the components of your electronic device. Check the manufacturer's instructions, if necessary.

Too much of either amperage or voltage will destroy the components, while too little will not allow the device to work correctly. Most have a safe range; aim for the center so your input power can vary somewhat. 3 Use a transformer to step down the output from high-voltage AC to low-voltage AC. Electrical current enters the primary coil of the transformer and induces a current in the secondary coil, which has fewer coils, resulting in a lower voltage. Little power is lost in this process because the amperage increases in relation to the decrease in voltage. 4 Run the low-voltage AC through a rectifier. A rectifier usually consists of 4 diodes arranged in a diamond shape -- a type called a bridge rectifier. A diode only allows current to pass in 1 direction; the diamond configuration allow 2 diodes to pass the positive half of the current and the other 2 diodes to pass the negative half. The output of both sets is a current that climbs from 0 volts to the maximum positive voltage. 5 Add a large electrolytic capacitor to smooth out the voltage. A capacitor stores an electrical charge for a short time and then releases it slowly.

The input from the rectifier resembles a string of humps; the output of the "smoothing capacitor" is a somewhat steady voltage with ripples. For devices that only need a low current, you can create a regulator with a resistor and a zener diode, which is designed to break down when a certain voltage is reached, allowing current to pass through it. The resistor limits the current. 6 Pass the output of the smoother through a regulator. This smooths out the ripples and creates a very steady current that will operate your electronic device without damaging it. Regulators are integrated circuits and can either have fixed or variable output voltages. Although regulators include protection against excessive current and heat, yours may still require that you attach a heat sink to keep it from becoming too hot. Community Q&A What is the difference between AC and DC? wikiHow Contributor AC is alternating where the electrons simply move back and forth. DC is the electrons moving in a straight, continuous flow. What's the difference between a DC and AC converter? wikiHow Contributor The converter is used only to change AC into DC. To change the current from DC to AC, you need an inverter. Can I buy a power cord that is an AC to DC converter?

wikiHow Contributor This material is based upon work supported by the National Science Foundation under Grant No Brush A conductive block used to make sliding contact with an armature. Byte A group of eight binary bits, commonly used to represent digital data. Cable A stranded conductor or group of individual conductors insulated from each other. Capacitance (C) The ability of two conductors separated by an insulator to store an electrical charge; measured in farads (F). Capacitive reactance (XC) The opposition that a capacitor offers to alternating current. This opposition, in the form of a counter electromotive force (cemf),is expressed in ohms. Capacitor A device designed to provide a specific amount of capacitance. Cell A device that transforms one form of energy into electrical energy. An example would be a chemical dry cell commonly used in flashlights (D, C, AA, AAA) and other electric devices. These are often referred to as batteries. Central processing unit (CPU) The part of a computer that performs the arithmetic, logic, and control functions. Circuit An arrangement or connection of circuit devices and components to perform a specific objective.

In the simplest form it would require an energy source, a load to transform the energy into the desired task, and conductors to connect the source to the load. In most applications a control device (switch) would be included and may also include a protective device. Common example of a simple circuit would be a flashlight. Circuit breaker A circuit protection device that opens the circuit automatically when an overload or short circuit occurs. Closed circuit A circuit that provides a complete path for current. Coil A wound spiral of two or more turns of insulated wire, used to introduce inductance into a circuit, produce a magnetic field from current flow, or to respond to a changing magnetic field by producing a voltage or mechanical motion. Component/s In electronics, a general term to refer to a part or parts of a circuit without reference to specific names. Commutator A cylindrical arrangement of insulated metal bars connected to the armature coils of a direct-current electric motor or generator, providing a unidirectional current from the generator or a reversal of current into the coils of the motor. Conductance (G) The ability of a conductor to allow the flow of electrons. Measured in Siemens (S). The reciprocal of resistance.

Conductor A low-resistance material to provide a path for current. Used to interconnect components in a circuit. Conventional current A direction flow assignment that has current flowing from positive to negative. Coulomb Base unit of electrical charge equal to 6.25 X 1018 electrons. Named for Charles Coulomb, the French physicist who pioneered research into magnetism and electricity. He also formulated Coulomb's law which states that the force of attraction or repulsion between two charged bodies is equal to the product of the two charges and is inversely proportional to the square of the distance between them. F= Q1 x Q2/d2 Crystal A natural or synthetic crystalline material having piezoelectric properties. As a transducer, used to convert dynamic pressures (vibrations) to ac electricity or change ac electricity into vibrations. Current (I) The rate of flow of electrons through a conductor or component; measured in amperes. The symbol (I) stands for intensity of the electron flow. Cycle One complete wave of alternating voltage or current. Dielectric A nonconductor of electricity. An insulator that is capable of concentrating electric fields. Difference of potential See electromotive force and voltage.

Digital Generally in electronics, refers to signals, devices, or circuits that are binary, meaning they only have two states (high or low, 1 or 0, on or off). The branch of electronics dealing with such signals and their circuits. Digital-to-analog converter (D/A) A circuit that converts a binary signal to an equivalent analog form. Diode A semiconductor device that only allows current to pass through it in one direction, cathode to anode. Also, a classification of semiconductor devices having only one junction. Examples include: rectifier, zener, varactor, and tunnel diodes. Direct Current (dc) Current from a power source that continually flows in the same direction. An electrical source of constant polarity. Duty Cycle The ratio of pulse width to period, indicates the percentage of time a pulse is present during a cycle. Electricity The physical phenomena arising from the behavior of electrons and protons that is caused by the attraction of particles with opposite charges and the repulsion of particles with the same charge. The physical science of such phenomena. Also, electric current used or regarded as a source of power. Electric energy The energy carried by free electrons from a source to a load. Also, the potential energy of a stationary charge.

Electric power (P) The rate at which energy is consumed in a circuit or load. Measured in watts (W). Electrolyte A chemical solution used in cells and some capacitors to produce an electrically conductive medium. Electrolytic capacitor A capacitor whose dielectric is formed through the reaction of an electrolyte and its electrodes. Electromagnet A device that produces a magnetic field as the result of current flow through a coil of wire. Electromechanical A classification of actions or devices whereby a mechanical action is caused by the forces of attraction or repulsion created when current flow generates magnetic fields (electromagnetic). Electromotive Force (emf) The force or electrical pressure that has the potential to cause electron flow in a circuit. Also called voltage, potential difference or difference of potential. Measured in volts (V). Electrostatic field An electric field produced by stationary charges. Farad (F) The basic unit of measurement for capacitance. One farad is that capacitance that will store one coulomb of charge when the charging force is one volt. Since the farad is a very large unit, capacitance will more commonly be expressed as microfarad (uF) or picofarad (pF) values.

Named for Michael Farady, the British physicist and chemist who discovered electromagnetic induction and proposed the field theory later developed by Maxwell and Einstein. Field Effect Transistor (FET) A transistor type that uses voltage to control current through the device. See JFET and MOSFET. Filter A circuit designed to pass a specific frequency range while rejecting all others. Flux Generally refers to a magnetic line of force but may also describe an electric line of force. Frequency The number of cycles per second for a periodic waveform. Measured in hertz (Hz). Fuse A protective device designed to interrupt current flow (open) through a circuit when current exceeds a rated value. Gate A logic circuit performing a specific logic function. See AND, OR, NAND, OR and NOT. Gauss A unit of measurement for magnetic field. Generator A device that converts mechanical energy to electrical energy. Ground The common return path for current in an electrical circuit. Serves as a reference point for measuring all other potentials in a circuit. Generally assumed to be at zero potential with respect to the earth. Other than earth references may be used such as the chassis of an automobile (chassis ground) or some arbitrary point in a circuit (circuit ground) like the negative side of the power source.

Heat sink A device attached to a component to aid in the dissipation of heat. Henry (H) The unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second. Named for Joseph Henry, an American physicist who performed extensive studies of electromagnetic phenomena. Hertz (Hz) A unit of frequency equal to one cycle per second. Named for Heinrich Hertz, a German physicist who was the first to produce radio waves artificially. Impedance (Z) Opposition to current flow from the combined effects of resistance and reactance measured in ohms (S). Inductance (L) The property of a circuit that opposes a change in current. Also, the property of a circuit to store energy in the form of a magnetic field and release it back into the circuit at a later time. Inductive Reactance (XL) The opposition that an inductor offers to alternating current. This opposition, in the form of a counter electromotive force (cemf), is expressed in ohms. Inductor An electrical device designed to provide a specific amount of inductance; measured in henrys (H).

Insulation Nonconductive material used to cover wires and components to prevent shock and short circuits. Insulator A material that has a high resistance to current flow. Integrated Circuit (IC) The placement of numerous components and circuits on to a silicon chip. Internal resistance The resistance within a power source. Inverter A logic devise (NOT function) whose output is always opposite the input. Also refers to a devise that converts dc to ac. Junction Field Effect Transistor (JFET) A transistor type made by diffusing a gate region into a channel region. Voltage applied to the gate controls current in the channel by either depleting or enhancing the channel. Joule The basic unit of electrical, mechanical, and thermal energy. As a unit of electrical energy it is equal to the energy carried by 1 coulomb of charge being propelled by an electromotive force of 1 volt. Named for James Joule, the British physicist who established the mechanical theory of heat and discovered the first law of thermodynamics. Kilo (k) Metric prefix for units of measurement equal to thousands (1000 or 103). As an example: 1 kilohertz (kHz) equals 1000hz.

Kilowatthour (kWh) Unit of energy consumption equal to 1000 watt-hours or the energy consumed at the rate to one kilowatt (kW) for a time of one hour. Equivalent to 3,600,000 joules. Generally used to specify a large energy consumption over a specific time interval. Residential energy is usually priced at the number of kilowatt-hours used for a month. Kirchhoff, Gustav Robert The German physicist noted for his research in spectrum analysis, optics, and electricity. Developed fundamental DC circuit laws dealing with current characteristics in a parallel circuit and voltage characteristics in a series circuit. His current law states that the current entering a connection has to equal the current leaving that connection, and that the sum of the load currents has to equal the source current (or sum of source currents for multiple parallel sources) (IT = I1+I2+------+IN). His voltage law states that around any closed loop of series connected components, the sum of the voltage drops must equal the source voltage (or sum of source voltages for multiple series connected sources. (VT = V1+V2+ ------ +VN).

Lamp A light producing device consisting of a filament placed in a vacuum. Law of magnetic poles Like poles repel, unlike poles attract. Liquid crystal display (LCD) A display type using changes in reflectivity to generate various characters. Lenzï¿½s Law Basic law of electromagnetic induction which states that an induced voltage will have a polarity that opposes the current change that produced it. Light-emitting diode (LED) A semiconductor diode that emits light as current flows from the cathode to the anode across its PN junction. Linear A circuit or component where the output is a straight line (direct proportion) function of the input. Load A device or apparatus that uses the energy of a circuit to perform work. May also refer to the power used by a device, machine, or a combination of many. Magnet An object which produces a magnetic field in the surrounding space. Magnetic field The detectable magnetic flux issuing from a magnet or electromagnet. Magnetic poles The two points of strongest concentration of magnetic flux around a magnet or electromagnet. By assignment the flux leaves the north pole and returns to the south pole. Magnetic saturation The point where an increase in magnetic force produces no further magnetic effect in a magnetic material.

The material can have no further increase in flux. Iron, nickel, cobalt, and their alloys are considered to be magnetic materials. Magnetism The physical phenomena exhibited by magnets and electric current flow that is represented by lines of force. Mega (M) Prefix for units of measurement equal to millions (1,000,000 or 106). Memory The part of a computing device where data and instructions are stored. See RAM and ROM. Metal oxide field-effect transistor (MOSFET) Also called insulated gate field effect transistor (IGFET). A transistor type that uses an electric field to control conduction. Micro (u) Prefix for units of measurement equal to millionths (1/1,000,000 or 10-6). Microprocessor A CPU that is manufactured on a single integrated-circuit (IC) chip. Milli (m) Prefix for units of measurement equal to thousandths (1/1000 or 10-3). Modem Abbreviation for modulator-demodulator. A device that converts data from one form into another, as from one form usable in data processing to another form usable in telephonic transmission.

Multimeter An instrument that can measure current, voltage, and resistance on various ranges. Many multimeters can measure other circuit values such as frequency and capacitance. May have digital (DMM) or analog displays (VOM). NAND gate or logic Stands for NOT-AND. Gives an inverted output of AND logic. Negative For sources, implies the terminal that has an excess of electrons. Also, can imply the polarity of a point in a circuit in respect to some other point. Nonlinear A circuit or component whose output versus input graph is not a straight line. NOR gate or logic Stands for NOT-OR. Gives an inverted output of OR logic. North-seeking pole That pole of a magnetic which points to the earthï¿½s north pole when free to turn. Nortonï¿½s theorem A method of reducing a complex network of bilateral (conducts equally well in both directions) components to one current source and one shunt resistance across the load terminals. Ohm (S) The unit of measurement for resistance. Named for Georg Simon Ohm, the German physicist noted for his contributions to mathematics, acoustics, and the measurement of electrical resistance.

One ohm is that resistance that limits the current to one ampere when a potential of one volt exist across its terminals. Ohmï¿½s law Very basic circuit law that defines the relationships between current, voltage, and resistance in a DC circuit. Ohmï¿½s law states that current is directly proportional to voltage and inversely proportional to resistance. (I = V/R) The other forms of the formula are V = IR and R = V/I. Ohmmeter An instrument for measuring resistance. Operational Amplifier (Op Amp) A highly stable direct coupled amplifier resistant to oscillation. May be packaged in an IC format. OR gate or logic Generates a logic 1 if any one of its two or more inputs are 1. Oscillator A circuit that converts dc power into ac signals with constant frequency. Also, an instrument that generates ac signals whose frequency and amplitude can be varied. These are also referred to as signal generators. Oscilloscope An instrument that displays a plot of voltage over time. Often referred to as a scope. Overload A load in excess of the design limit for a circuit. Parallel circuit A circuit with two or more loads (or sources) connected such that all have the same voltage but different currents.

Each load can be operated independent of the others. Parallel sources should have equal voltage ratings. Period The time in seconds that is required to complete one cycle of a waveform. Permeability The ability of a magnetic material to conduct magnetic lines of force. Phase A time relationship between two electrical quantities. Polarity For electrical charge, the indication of a charge as either positive (+) or negative (-). Voltage at a point would be indicated as being either positive or negative with respect to some other point. For magnetic poles, the indication as either north or south. Positive For sources, implies the terminal that has a deficiency of free electrons. Also, can imply the polarity of a point in a circuit in respect to some other point. Potentiometer A three-terminal resistor with an adjustable center connection generally used to control voltage; widely used for volume control in radio and television receivers. In this sense, also called a Pot. Power The rate at which energy is consumed. In electronics it refers to the consumption of electrical energy in joules over time; measured in watts. Power factor(PF) The ratio of true power to the apparent power in a circuit, especially those that are not purely resistive. It is also equal to the cosine of the phase angle for the circuit.

Power supply Generally, a device or circuit used to convert alternating current (ac) of specific voltage to one or more direct current (dc) values of specific voltage and current ratings. May have variable voltage ability in some instances. May also refer to a device that converts a specific dc value to another dc value (dc to dc converter). Primary cell A device that uses up its ingredients to convert chemical energy to electrical energy and therefore can not be recharged. Primary winding The input winding to a transformer. Printed circuit (PC) board A fiberglass board with copper foil as the conductors to interconnect the attached electrical components. Random-access memory (RAM) A read/write memory that allows date storage (Write) and data retrieval (Read) to any location in any order. Considered to be temporary (volatile) in that the contents are lost if power is turned off. Reactance Opposition to current offered by capacitors and inductors in the form of a counter-electromotive force (cemf), but expressed in ohms. Reactance does not consume power but gives the appearance that it does.

Read only memory (ROM) A classification of non-volatile memory that has its contents built in at time of manufacturer and which cannot be changed and cannot be lost if power is turned off. Variations include Programmable (PROM) and Erasable Programmable (EPROM) which has provisions for user programming. Rectifier A solid state device that converts alternating current to pulsed direct current. Relay An electromechanical device that uses electromagnetism to mechanically switch electrical circuits. The output contacts are designed to be either normally open (NO) or normally closed (NC). Some relays provide both arrangements and multiple switches. Resistance (R) The opposition to current flow in a circuit; measured in ohms. Resistor An electrical component designed to provide a specific resistance. Available in many formats such as fixed, tapped, and variable. See potentiometer and rheostat. Resonance A circuit condition when the inductive reactance (XL) equals the capacitive reactance (XC). A resonant circuit is one that has been tuned to that condition and resonant frequency is that frequency that resonance occurs in a circuit and provides a maximum output for one of its circuit variables.

Rheostat A two-terminal resistor with an adjustable center connection and one end connection generally used to control current. Ripple The small amount of ac voltage that still remains in the output of a dc power supply. RMS Root mean square The value of an ac sine wave that indicates its equivalent dc value for producing heat. Also called the effective value, it is equal to 70.7% of the maximum value (peak value) for the waveform. Schematic or schematic diagram A drawing dipicting how the components are connected using standarized symbols. Secondary cell A device whose ingredients convert chemical energy to electrical energy but can be recharged. Secondary winding The output winding of a transformer or one of several output windings. Series circuit A circuit arrangement of two or more loads (or sources) connected end-to-end only allowing for one current path. Therefore, all components have the same current but can have different voltage. An open at any point or in any component interrupts current flow for all. Semiconductor Any of various solid crystalline substances, such as germanium or silicon, having electrical conductivity greater than insulators but less than good conductors. In electronics these are generally doped to from either N type or P type material.

These materials are the foundational material for diodes and transistors. Short circuit An undesirable low resistance path between two points in a circuit. Siemen (S) The unit of measurement for conductance. Named for Ernst Werner von Siemens, a German engineer who made notable improvements to telegraphic and electrical apparatus. Silicon-controlled rectifier (SCR) See thyristor Sine wave A waveform whose instantanous amplitude is a function of the sine of the angle of rotation for that instant. The output waveform produced by rotating a loop in a magnetic field, and the output of an oscillator generating a pure frequency. Solar cell A device that converts light energy to electrical energy. Also called a photovoltaic cell. Solder Any of various fusible alloys, usually tin and lead, used to join metallic parts. In electronics used to connect components to PC boards or to aid the conductivity and mechanical junctions of connections and splices. Solenoid Electromechanical device that use electromagnetism to produce a mechanical operation. Solid-state The term that describes components or circuits that use semiconductors technology. Source General term to describe devices that provides electrical energy at their output terminals to operate a circuit.

Examples: battery, solar cell, generator and alternator, or power supply. Static electricity A stationary electrical charge on an object. Stator The electromagnetic part of a motor or generator that does not rotate. Stepper motor A motor type driven with digital codes that moves in discrete angular increments with each code change. Superposition theorem A method for analyzing a complex network of bilateral (conducts equally well in both directions) components having multiple sources. Surge A very rapid increase of current or voltage. Switch A device used to open (turn off) and close (turn on) electrical circuits that can be designed to operated by numerous actions such as toggle, slide, and pushbutton actions. Standard configurations include SPST, SPDT, DPST, and DPDT. Terminal A connection point for electrical components or conductors. Thermistor A resistor made of semiconductor material having resistance that varies rapidly and predictably with temperature. Used as a temperature sensor, the resistance varies inversely with temperature. Thermocouple A thermoelectric device used to measure temperatures accurately, consist of two dissimilar metals joined so that a potential difference is generated that is representative of the temperature of the junction.

Theveninï¿½s theorem A method of reducing a complex network of bilateral (conducts equally well in both directions) components to one voltage source and one resistor in series with the load terminals. Thyristor A broad classification of semiconductor devices used as electronic switches. Examples include diacs, SCRs, and triacs. Tolerance Used to describe the allowable variance in a measurement or a components value. Transducer A device used to convert input energy of one form into output energy of another. Transformer A device used to transfer electric energy from one circuit to another, especially a pair of multiply wound, inductively coupled wire coils that effect such a transfer with a change in voltage, current, phase, or other electric characteristic. Generally used to convert one voltage-current relationship to another. Step-up transformer, increase the voltage while decreasing the current, and step-down transformer decrease the voltage while increasing the current. Transistor A small electronic semiconductor device having at least three electrical contacts, used in a circuit as an amplifier or a switch. See: BJT, JFET, MOSFET. True power The actual power consumed by a circuit; measured in watts. Volt (V) The unit by which an electromotive force or voltage is measured.

Named for Alessandro Volta, the Italian physicist who invented the first electric battery (1800). Voltage (V) Same as emf. The force or electrical pressure that has the potential to cause electron flow in a circuit. Voltage divider A series circuit that divides voltage. Voltage drop The difference in potential between two points caused by current flow through a component. Voltmeter An instrument used to measure voltage. Watt (W) The unit of measurement for power. One watt equals to the work done when one joule is used per second. Named for James Watt the British engineer and inventor. Watt-hour (Wh) Unit of energy consumed at the rate of one watt (W) for a time of one hour. Equivalent to 3,600 joules. Wheatstone Bridge An instrument or a circuit consisting of four resistors or their equivalent in a series-parallel arrangement, used to determine the value of an unknown resistance when the other three resistances are known. Wiring diagram A graphic representation of how circuit components are connected. Zener Diode A semiconductor device designed to operate at a fixed voltage as a voltage regulator.

Question: What is a device that allows electric current to pass through it in one direction only, used for converting AC to DC?
Answer: Rectifier