# Electronics – Electrical Unit Definitions

Definitions of basic measurement units in electricity and electronics

## Ampere (A)

Unit of measurement of electric current. Is the amount of charge that flows through a conductor in a unit of time. I = Q / t

**Ampere** is the electric current (I) that produces a force of 2 x 10^{-7}newton per meter between two parallel conductors separated by 1 meter. 1 A = 1 coulomb / second. 1 A = 1000 mA (milliampere). See also:

## Coulomb (C)

**Coulomb** is the measuring unit of the electric charge. Q load passing through a point in one second when the current is 1 ampere. 1 Coulomb = 6.28×10^{18} electrons.

See: Coulomb’s Law

## Joule (J)

**Joule** is the work (W) made by the force of one Newton acting over the distance of 1 meter.

## Watt (W)

**Watt** is the power unit. Power (P) required to perform a work at a rate of 1 joule per second.

See: Joule’s Law

## Farad (F)

**Farad** is the capacitance measuring unit. Farad is the capacitance (C) where the load of 1 coulomb produces a voltage of 1 volt. See also:

- Capacitor classification
- Electrolytic Capacitor
- Capacitors Codes
- JIS Code capacitors

## Henry (H)

**Henry** is the inductance measurement unit. Henry is the inductance (L) where 1 volt is induced by a change of 1 ampere per second. See also:

- Iron Core Inductor
- Air core inductor
- Series and parallel inductors
- Inductors and currents, quality factor
- Inductor: unit-step response

## Ohm (Ω)

Unit of measurement of the electrical resistance, represented by the capital Greek letter (Ω) omega. **Ohm** is the resistance that produces a voltage of 1 volt when it is traversed by a current of 1 ampere. See also:

- Electrical Resistance
- Variable resistor (potentiometer, rheostat)
- Wirewound resistor
- Resistors color coding
- Measuring ranges for resistors on a VOM
- Measure resistance of low value
- Measure sensitive resistors

## Siemens (S)

**Siemens** is the unit of measure of the conductance (G). Siemens is the conductance which produces a current of 1 ampere when a voltage of 1 volt is applied. It is the reciprocal of the ohm, formerly called mho.

See also: resistance / conductance

## Volt (V)

**Volt** is the unit measuring the electrical potential difference or voltage. Voltage is the potential difference between two points in a conductor carrying a current of 1 ampere when the power dissipated between the two points is 1 watt.

See also: Voltage. Electrical Potential difference.

## Hertz (Hz)

**Hertz** is the number of complete cycles of a wave in a unit of time. 1 Hertz = 1 cycle / sec. See also: Alternating Current (AC)

## Radian

**Radian** is the angle which covers the circumference portion which is equal to the length of the radius of the circle.

## Angular frequency (w)

**Angular frequency** is radians per second. w = 2nf. (n = pi). see also: What is a radian? – Angular frequency

## Time (t)

**Time** measurement unit (Sec) See: The time constant