# Electronics/Definitions

Electronics | Foreword | Basic Electronics | Complex Electronics | Electricity | Machines | History of Electronics | Appendix |
Get ideas from here:
http://en.wikipedia.org/wiki/List_of_electronics_topics
(BUT WE ONLY WANT THINGS THAT MATTER TO A TWO YEAR LEVEL. No "quadrature amplitude modulation" or anything like that.)
SI Units and derived units
Definitions in Alphabetical Order:
Another order could be definitions by subject such as DC, AC, radio, integrated circuit, etc.

## AC

    Alternating current. Consists of a periodic oscillation between two different voltages. Usually said to look like a sine wave, but is not always.

## AM

    Amplitude modulation. In radio communications, a signal controls the amplitude of a carrier wave that is at a much higher, constant frequency. The carrier wave is filtered out and a loudspeaker plays based on the amplitude of the signal.

## Ampere (A)

    The SI unit for current I. (Commonly spoken as "amps", "milliamps", etc.) The ampere is officially defined as that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed one meter apart in vacuum, would produce between these conductors a force equal to 2×10$^{-7}$ newton per meter of length. There is another definition which is based on the deposition rate of silver (in electrolysis?), which is much easier to measure. The other electronics units are derived units based on the ampere definition.

## Amplify

    To increase the strength of the signal. Often an "amplifier" is used to pass a signal with both an increase or a decrease in gain.

## Anode

    An electron collector. Means up the path from a negative to a positive voltage. An anode has a more positive voltage relative to a cathode.

## Attenuate

    Decrease the strength of a signal.

## Band-Pass Filter

    An analog filter that absorbs low and high frequencies (f) but allows a band of frequencies in the middle to pass through.

## BJT

    Bi-polar junction transistor. A transistor in which the resistance of the channel is controlled by a current at the gate. Can be thought of as a current-controlled resistor. FET is the other major type of transistor.

## Capacitor

    An electronics component that stores energy in the form of electric charge (static electricity). It resists a sudden change in voltage.

## Cathode

    An electron emitter. A cathode has a more negative voltage relative to some other place.

## Choke

    Another name for an inductor, specifically referring to those used in power regulation.

## CMOS

    Complementary metal oxide semiconductor. Complementary means that it has N-channel and P-channel transistors. Metal oxide is the type of gate. CMOS is a type of Integrated Circuit (IC) that is voltage based, since it is made of FETs. Digital circuits tend to use very little current, because the paths for current flow are effectively open or closed circuits except during the transition between states.

## Coil

    A helix of wire (the same shape as a spring or Slinky). Its height, width, thickness, and material can all vary. Used as an inductor. The loops of wire can overlap.

## Condenser

    Another name for capacitor.

## Conductance

    The inverse of resistance. Measured in siemens (obsolete name mhos), which are the inverse of ohms. 1 S = 1/Ω = 1 A/V = 1 A$^2$/W

## Coulomb (C)

    The SI unit for electric charge Q. Defined in terms of the ampere. 1 coulomb is the amount of electric charge carried by a current of 1 ampere flowing for 1 second. It is also about 6.24×10$^{18}$ times the charge on an electron. 1 C = 1 A·s

## Current

    The drift of electrons in an electric field. This is perceived as a flow. It is measured in amperes.

## Cycles per second (cps)

    An obsolete name for hertz, the standard SI unit. As the name implies, a measurement of frequency in full cycles of a wave per second. The unit cps (or kilocycles, megacycles, etc.) is more often seen in older documents.

## dB

    Decibel. Used to measure logarithmic ratios like signal to noise ratio (SNR), total harmonic distortion (THD), volume relative to a nominal level. Similar to percent (%) in that it has no units. dB SPL is used to measure sound levels relative to 20 micro-pascals (µPa). dBu is used to measure voltage relative to 0.775 V.

## DC

    Direct current. A constant voltage and a constant current flow in one direction.

## Diode

    A one way valve for current. Semiconductor diodes typically have a voltage drop of 0.6 V (silicon) or 0.2V (germanium) when conducting in the forward direction.

## EMF (E)

    Electro-Motive Force. A force for moving electrons. See Voltage.

## Ethernet

    is a family of frame-based computer networking technologies for local area networks (LAN). It defines a number of wiring and signaling standards for the Physical Layer of the standard networking model as well as a common addressing format and a variety of Medium Access Control procedures at the lower part of the Data Link Layer.

## Farad (F)

    The SI unit for capacitance (C). A capacitor is one farad if it has a coulomb (1 C) of charge on it with a voltage separation of a volt (1 V). 1 F = 1 C/V

## FET

    Field Effect Transistor. Can be thought of as an Electric Field Transistor. A transistor in which the voltage at the gate controls the resistance of the channel. (i.e. a FET has voltage-controlled resistance.) BJT is the other major type of transistor.

## FM

    Frequency modulation. Changing the frequency of a carrier signal to represent the amplitude of the original signal.

## Forward Biased

    The voltage polarity through a part which causes it to conduct current.

## Frequency (f)

    The number of revolutions (cycles) per unit time. Usually expressed in either radians per second or cycles per second (Hz).

## Gain

    A multiplier of voltage or current.

## Ground

    Ground is defined as the point in the circuit which is at zero voltage. Voltage is relative, and is the same throughout a conductor, so any point in the circuit can be defined as ground, and all other voltages are referenced to it. Usually it is defined as the most negative point in the circuit, for convenience. Sometimes it is defined in the middle of two bi-polar rails, for "balanced" circuits. In many cases this circuit point is connected to the Earth (Ground) by some buried conductor.

## Henry (H)

    The SI unit for inductance. 1 H = 1 Wb/A

## Hertz (Hz)

    The SI unit for frequency. One Hz is one cycle per second. 1 Hz = 1/s

## High-Pass Filter

    An analog filter that absorbs low frequencies (f) but allows high frequencies to pass.

## Horsepower (hp)

    The amount of force F a horse can exert. I don't think it is related to horses anymore. 1 hp = 746 W

## IC

    Integrated circuit. A circuit constructed on one chip of semiconductor, rather than as discrete components.

## Impedance

    A more generalized form of resistance. The impedance of a device varies with the frequency of the electricity applied. A perfect resistor will have a constant impedance for all frequencies. Capacitors and inductors have varying impedances at different frequencies. Measured in ohms.

## Inductor

    An inductor is a device that stores energy in a magnetic field. It opposes a sudden change in the flow of current. A solenoid is usually shaped like a spring or a Slinky.

## Joule (J)

    The work required to exert a force of a newton (1 N) for a meter (1 m). 1 J = 1 N·m

## LASCR

    Light activated silicon controlled rectifier. A light activated SCR.

## LDR

    Light dependent resistor. As light intensity increases, its resistance decreases.

## Length (l)

    Distance is measured in meters (m).

## Low-Pass Filter

    An analog filter that absorbs high frequencies (f) but allows low frequencies to pass.

## Magnetron

    A special form of vacuum tube, typically used as the microwave emitter in a microwave oven, or in Radar systems.

## Meter (m)

    The SI unit for distance. The distance light travels in 1/299,792,458 second.

## MOSFET

    Metal-oxide-semiconductor field effect transistor. An FET that uses a thin layer of oxide (usually silicon) to insulate the gate terminal from the underlying channel

## Ohm (Ω)

    A measure of resistance or impedance. 1 Ω = 1 V/A = 1 W/A$^2$

## Op-amp

    Short for operational amplifier. An op-amp amplifies the voltage between its two inputs.

## Oxidation

    A reaction where something loses electrons. Given that oxygen will strip electrons from most elements, this has historically meant a reaction involving oxygen. A cathode (electron emitter) is constantly oxidized as it looses electrons.

## PCB

    Printed circuit board. This is a piece of plastic or fiberglass with copper attached. The copper is typically chemically etched away to leave "traces" for the electricity to be conducted through. Other electrical components are soldered to the traces.

## Period

    The time between cycles of a periodic wave.

## PM$^1$

    Phase modulation. Sending information by modifying relative phases.

## PM$^2$

    Pulse modulation. Sending information in binary pulses.

## Power

    Voltage times current. The amount of work being done by a circuit.

## Rectify

    Convert AC current to DC current.

## Redox

    A reaction where oxidation and reduction take place. A cathode (electron emitter) is oxidized (loses electron). The electron travels and is absorbed by an anode (electron acceptor) that is reduced (gains electron).

## Reduction

    A reaction where something gains electrons. In gaining electrons its charge value is reduced. An anode (electron acceptor) is constantly reduced as it gains electrons.

## Resistance

    Properties of a circuit that impede the flow of electrons. Resistance converts electrical energy into photons that are given off as waste heat. Resistance is measured in ohms.

## Reversed Biased

    The inverted voltage polarity on a part.

## Root-Mean Squared (RMS)

    The effective DC value for an AC value.

## SCR

    Silicon-controlled rectifier.

## Second (s)

    The SI unit for time.

## SI

    The standard system of units.

## SMT

    Surface mount technology. This is a circuit built on a PCB with the components soldered directly to pads on the surface, without going through the board. The components and boards are usually much more compact than through-hole boards.

## Speed of light

    Varies depending on the medium it is traveling through. Maximum speed c of 299,792,458 m/s is only in a perfect vacuum. Light has been slowed down to less than 17 m/s (~40 mph) in special mediums.

## Speed of wave propagation (v)

    Speed that an electromagnetic wave travels through air, cables, or wires. A typical speed for a typical coax cable is (2/3)·c.

## Thermistor

    Temperature based resistor. As temperature increases resistance decreases.

## Thyristor

    A type of electronic switch. It has two states which are triggered by another voltage or current. SCRs and switching transistors are examples of thyristors.

## Tesla (T)

    Unit of magnetic flux density. 1 T = 1 Wb/m$^2$

## Through-hole

    This means the circuit is built on a PCB with holes drilled in it for the component leads to go through. The leads are soldered on the other side of the board.

## Time (t)

    The symbol for time in seconds (s).

## Transformer

    Used to raise or lower the AC voltage between two circuits. This is based on the ratio of turns between the two coupled inductors. Transformers operate by way of induction between two inductors.

## Triode

    A three-element vacuum tube.

## TTL

    Transistor-Transistor Logic

## Voltage AC (VAC)

    AC Voltage

## Voltage-amperes reactive (VAR)

    Reactive voltage.

## Variac

    A type of transformer with a movable tap to provide a variable output voltage. Also "Powerstat".

## Volt (V)

    A potential due to an electric field. One volt is defined as the potential difference across a resistor that is passing one ampere and dissipating one watt. 1 V = 1 W/A

#### Volt

    (changed to demonstrate subsection headings)
    A potential due to an electric field. One volt is defined as the potential difference across a resistor that is passing one ampere and dissipating one watt. 1 V = 1 W/A

##### Voltage (V)

    An electric field between two charges. Similar to gravity this acts as an electric potential. Measured in volts.

##### V$_{CC}$

    Common-collector voltage source (+). This is an alternate label for the power supply in electronic diagrams for BJT-based circuits such as common-collector amplifiers. (There is also V$_{EE}$, V$_{DD}$, V$_{SS}$ do we want one for each?) That might work if they were grouped together.
   * http://encyclobeamia.solarbotics.net/articles/vxx.html
   * http://www.control.com/1026184337/index_html

##### Watt (W)

    A measure of power (P). A watt is a joule (1 J) of work done in a second (1 s). 1 W = 1 J/s

##### Wavelength (λ)

    The distance between two peaks of a wave.

##### Weber (Wb)

    Unit of magnetic flux. 1 Wb = 1 V·s

## to be merged

superfluous stuff from "overview of electronics", which should be merged in with these definitions:
Charge: Particles can have three possible types of charge: positive, negative, or neutral (no charge). Electrons are negatively charged, protons are positively charged, and neutrons are (surprise!) neutral. Opposite charges tend to attract, while particles with the same charge (both positive or negative) tend to repel.
Electricity: the flow of electrons.
Electronics: is the study of gadgets that use electricity, typically creating or handling signals, not just switching power.
??? are devices which take in input, perform some function, and return some output, through the use of electricity.
Circuit: The path electrons take as they are pushed by some power source, flow through various electrical components in a gadget, and return to the power source.
Electric Field: field created by the presence of charge. The field represents the force that would be felt by a positive charge.
Voltage: Accelerates charge.
Voltage is a gravity-like potential due to the separation of a negative and a positive charge. Voltage accelerates negatively charged electrons from the negative to the positive charge, and accelerates positive charged protons and ions the other way. Pushing accelerates the charges in what is known as current.
Resistance: When moving electrons (current) collide with atoms, energy is given off as heat. Resistance is the measure of a material's tendency to cause this type of energy loss. Resistance acts to limit the flow of current due to a given voltage. As the resistance becomes infinite the current stops flowing and becomes an open circuit. When there is no resistance the circuit shorts and the current becomes infinite. (Current 'prefers' the path with the lowest possible resistance.)
* Air has higher resistance than wire.
Resistor: A device whose primary use is to provide resistance.
Short Circuit: there is no resistance between two points. Current flows without a change in voltage.
Open Circuit: there is infinite resistance between two points. Current is unable to flow, but there is still a voltage between the two points.
Voltage Source creates a voltage, which creates a current.
Current Source, which creates a current and a voltage for the current.
Voltage Drop When the current goes through resistance it loses some of the push of the voltage.
When the current comes to an intersection it has multiple paths it can take and flows according to its resistance.
Permittivity: (ε) A measure of how much energy a material absorbs in response to an electric field. Materials (ε$_r$) absorb more energy than the vacuum (ε$_0$). The permittivity of a material is known as its dielectric constant.
Cell: Two materials with a voltage difference between them.
Capacitor: Two metal plates with a gap between them. Voltage causes charge to drain from one plate and accumulate on the other plate. This charge separation creates a voltage in the capacitor that opposes the other voltage and stops the flow of current. When a dielectric is placed between the plates it weakens the electric field between the plates and allows more charge to accumulate.
Capacitance: Any two pieces of conducting material separated by some distance have capacitance. Simply, a measure of the tendency of some configuration of metal to act as a capacitor.
Inductor: A coil of wire. Current starts to flow through the wire and creates a magnetic field. This magnetic field creates an opposing magnetic field which stops the current through the wire. Over time the inductor stops opposing current and turns into a wire.
Transformer Two connected inductors, which operate through mutual inductance. Current flows through the first inductor and creates a magnetic field that is fed to the second inductor. In response the second inductor creates an opposing magnetic field and current. Having a permanent magnet between the two inductors intensifies their magnetic fields.
Vacuum tube: An arrangement of two or more electrodes in a vacuum. Typically placed in a glass bulb to keep air from leaking in.
Triode: The first electrical amplification device. A triode is a type of vacuum tube with three connections:
* The cathode emits electrons.
* The anode accepts electrons.
* The 'grid, placed in the middle, which controls the flow of electrons from the cathode to the anode.
Diode: A 2 wire device that allows current to flow easily in only one direction.
Transistor: A 3 wire device, with one wire (the "base" or "gate") that controls the flow of electrons between the other 2 wires. Replaced vacuum tubes.
Light waves: (Electromagnetic waves)