How does an electric motor work?
An electric motor spins because a current-carrying wire in a magnetic field experiences a force (the motor effect).
GCSE Physics
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
In more detail
When current flows through the coil, each side of the coil sits in the magnetic field and experiences a force. The two sides carry current in opposite directions, so the forces act in opposite directions, creating a turning effect (moment) that rotates the coil. A split-ring commutator reverses the current direction every half turn, so the coil keeps rotating the same way instead of stopping.
Key points for the exam
- The force is given by F = BIL (field × current × length).
- The split-ring commutator swaps the current direction every half-turn to keep rotation continuous.
- Reversing the current or the magnetic field reverses the direction of spin.
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