Ohm's Law

This lesson covers Ohm's Law and the current–voltage characteristics of different components, as required by the AQA GCSE Physics specification (4.2.1.2 and 4.2.1.3). Understanding how current varies with potential difference is essential for predicting the behaviour of circuits.

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What Is Ohm's Law?

Ohm's Law states that:

The current through an ohmic conductor is directly proportional to the potential difference across it, provided the temperature remains constant.

This means that if you double the potential difference, the current will also double — as long as the temperature does not change. The relationship can be expressed as:

V = I x R

Where R (resistance) remains constant for an ohmic conductor at constant temperature.

Ohmic Conductors

An ohmic conductor is a component that obeys Ohm's Law. This means it has a constant resistance — the ratio V/I stays the same no matter what values of V and I are used.

Examples of ohmic conductors:

• A resistor (at constant temperature)
• A length of wire (at constant temperature)