# Current, resistance and potential difference

## Potential difference

The current through a component depends on both the of the component and the across the component.

Potential difference is a measure of how much energy is transferred to each Coulomb between two points in a circuit

### Measuring potential difference

To measure the potential difference across a component, a must be placed with that component in order to measure the difference in energy from one side of the component to the other. Potential difference is also known as and is measured in volts (V).

## Resistance

Jonny Nelson explains resistance with a GCSE Physics practical experiment

When a charge moves through a potential difference, electrical is done and energy transferred. The potential difference can be calculated using the equation:

potential difference = current × resistance

This is when:

• potential difference ( ) is measured in volts (V)
• current ( ) is measured in amps (A)
• resistance ( ) is measured in ohms (Ω)

One volt is the potential difference when one joule of work is done moving one coulomb of charge.

Conductors have a low resistance. Insulators have large resistances.

### Example

What is the potential difference if a current of 2 A flows through a resistance of 40 Ω?

= 2 × 40

= 80 V

Question

What is the resistance of a component if 12 V causes a current of 2 A through it?

= 6 Ω