Electrical current transfers energy around circuits. There are two types of current: direct and alternating.

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

To measure the potential difference across a component, a voltmeter must be placed in parallel 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 voltage and is measured in volts (V).

Potential difference is a measure of how much energy is transferred between two points in a circuit.

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

This is when:

- potential difference (
*V*) is measured in volts (V) - energy (
*E*) is measured in joules (J) - charge (
*Q*) is measured in coulombs (C)

One volt is the potential difference when one coulomb of charge transfers one joule of energy.

What is the potential difference between two points if 2 C of charge shifts 4 J?

- Question
How much energy is transferred when 3 C of charge moves through a potential difference of 6 V?

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

potential difference = current × resistance

This is when:

- potential difference (
*V*) is measured in volts (V) - current (
*I*) is measured in amps (A) - resistance (
*R*) is measured in ohms (Ω)

One volt is the potential difference when one coulomb of charge transfers one joule of energy.

Conductors have a low resistance. Insulators have a high resistance.

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

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