Electronics Glossary

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Stuck on a word? Find it here. Every term has a short, plain meaning. Type in the box to search, or tap a letter to jump.

A

Ammeter
a meter that measures current. It goes in series.
Amp (ampere, A)
the unit of current.
Analogue
a signal that changes smoothly through every value.
AND gate
output is 1 only when all inputs are 1.

B

Back-EMF
a sudden burst of voltage made when a coil is switched off.
Base unit
the plain unit with no prefix (for example Ω, A, V).
Buzzer
a part that makes a sound.

C

Capacitor
a component that stores charge.
Capacitance
how much charge a capacitor stores. Unit: farad (F).
Cell / battery
supplies energy — provides the p.d. (voltage).
Combinational logic
gates joined so one gate's output feeds the next.
Comparator (741)
a chip that checks which of two voltages is bigger.
Continuity
a test for whether a wire or joint lets current through.
Current
how much electricity flows. Unit: amp (A).

D

Digital
a signal with only two levels (high/low, 1/0).
Diode
lets current flow one way only.
Divider (voltage divider)
two resistors that split the supply voltage.

F

Farad (F)
the unit of capacitance.
Flyback diode
a diode across a coil that lets back-EMF flow away safely.
Frequency
how many waves per second. Unit: hertz (Hz).
Function
the job a component does.
Fuse
breaks the circuit if the current gets too high.

G

Gate (logic gate)
a part that gives a 1/0 output from 1/0 inputs.
Ground (0 V)
the 0-volt point you measure from.

H

Hertz (Hz)
the unit of frequency (waves per second).

I

IC (integrated circuit)
a "chip".
Input
a signal going into a circuit (for example a switch or sensor).

L

Lamp
a light output (filament).
LDR (light-dependent resistor)
a resistor whose resistance falls as light rises.
LED
gives out light when current flows the right way.
Logic probe
a tool that shows if a point is logic 1 or 0.

M

Mega (M)
prefix meaning × 1 000 000.
Micro (µ)
prefix meaning ÷ 1 000 000.
Milli (m)
prefix meaning ÷ 1000.
MOSFET
a voltage-controlled switch.
Motor
turns electrical energy into rotation.
Multimeter
a meter that measures voltage, current and resistance.

N

NAND gate
AND then inverted.
NOR gate
OR then inverted.
NOT gate
inverts the input: 0→1, 1→0.
Notch
the mark that shows the pin 1 end of a chip.

O

Ohm (Ω)
the unit of resistance.
Ohm's law
V = I R (voltage = current × resistance).
OR gate
output is 1 when any input is 1.
Oscilloscope
shows a signal as a trace on a screen.
Output
what the circuit drives (for example a lamp, motor or buzzer).

P

Parallel
components side by side on separate branches.
p.d. (potential difference)
another name for voltage.
Period
the time for one full wave. Unit: second (s).
Pin-out
which job each pin (leg) of a chip does.
Power
how fast energy is used (heat or light). Unit: watt (W).
Prefix
a letter in front of a unit that makes it bigger or smaller (k = × 1000).

R

Reference
the set level a comparator checks against.
Relay
a coil-worked switch for a separate, bigger circuit.
Resistance
how hard it is for current to flow. Unit: ohm (Ω).
Resistor
limits the current.

S

Series
components in one loop, joined end to end.
Solenoid
a coil that pulls an iron core in a straight line.
Speaker
turns a signal into sound.
Symbol
the drawing that stands for a component.

T

Test point
a spot you touch with a meter or probe to check a voltage or signal.
Thermistor
a resistor whose resistance changes with heat.
Time-base
the oscilloscope setting for time per division (s/div).
Tolerance
how far a resistor's real value can be from its label (for example ±5%).
Transistor
an electronic switch (or amplifier).
Truth table
a table of every input and the output it gives.

V

Variable resistor
a resistor you can adjust.
Volt (V)
the unit of voltage.
Voltage (p.d.)
the push that moves the current. Unit: volt (V).
Voltmeter
a meter that measures voltage. It goes in parallel.

W

Watt (W)
the unit of power.

X

XOR gate
output is 1 when the inputs are different.

Y

Y-gain
the oscilloscope setting for volts per division (V/div).