# A DC electric motor contains a rectangular coil of wire suspended between the poles of two permanent magnets. Describe how the motor produces a continuous rotation, including the role of the split ring commutator.

> Pearson Edexcel International GCSE Physics (4PH1) — 6.2 Electromagnetism · Describe · 4 marks

> A student builds a simple DC electric motor using a rectangular coil with 50 turns wound on a former. The coil is connected to a battery via a split ring commutator and carbon brushes placed inside a uniform magnetic field.

## Mark scheme (4 marks)

1. Direct current in the coil means the two sides perpendicular to the magnetic field experience forces in opposite directions
2. These opposite forces produce a turning effect / cause the coil to rotate
3. Without the commutator the coil would stop / reverse at the vertical position (every half turn the current direction in the coil would cause the forces to oppose rotation)
4. The split ring commutator reverses the direction of current in the coil every half turn, so the forces on each side remain in the same direction and rotation continues

## Key terms

- [split ring commutator](https://www.gradenine.co.uk/glossary/split-ring-commutator)

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-dc-electric-motor-contains-a-4407ea70) · Published by Druglandscape Ltd.