## What is Voltage?

In practical terms, voltage is the difference in electrical potential between two points in a circuit. The unit of measurement is the volt (V), which is a measure of the energy per unit charge.

Voltage is one of the properties of an electric field and can be measured in terms of:

- its relationship to a common point. This is usually with respect to ground (zero volts)

- the relationship between two points. This is usually known as the voltage across a device or the voltage across a circuit.

In physical terms, Voltage is the work required to move an electric charge between two points:

1 Volt is the force required to send one ampere of current through a resistance of one ohm.

## Some Formulae

- <math> V = \sqrt{PR} </math>

- <math> V = I \times R </math>

- <math> P = V \times R </math>

where *V* = potential difference (volts), *I* = current intensity (amps), *R* = resistance (ohms), *P* = power (watts).

## Voltage across Resistors, Inductors and Capacitors

Voltage cross a resistor (Resistor R):

- <math> V_R = IR_R \!\ </math>

Voltage across a capacitor (Capacitor C):

- <math> V_C = IX_C \!\ </math>

Voltage across an inductor (Inductor L):

- <math> V_L = IX_L \!\ </math>

Where *V*=voltage, *I*=current, *R*=resistance, *X*=reactance.