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Resistance - GCSE Physics Definition

Reviewed by: Leander Oates

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What is resistance?

In GCSE physics, resistance is opposition to the flow of current. Resistance occurs as the electrons flowing in a wire collide with the metal ions that make up the wire. In each collision, energy is transferred from the electron to the metal ion. Because there are so many electrons, the collisions cause the wire to heat up. The hotter the wire, the greater the resistance. 

A high resistance means that less current flows in the circuit. 

Diagram of electrical circuits: Top shows high resistance with dim bulb, green arrow; bottom shows low resistance with bright bulb, red arrow.
A low resistance in a circuit means that more current flows, when the resistance is higher, less current flows.

The resistance in a circuit or component can be calculated using the equation below:

V = IR

Where:

  • V = potential difference (or voltage), measured in volts (V)

  • I = current, measured in amps (A)

  • R = resistance, measured in ohms (Ω)

This equation may be presented in its rearranged form in some specifications.

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Leander Oates

Reviewer: Leander Oates

Expertise: Physics Content Creator

Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.

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