# A student places a straight wire connected to a battery inside a magnetic field. The wire lies at right angles to the field and experiences a force. The student then makes three separate changes to the setup. State what effect each of the following changes has on the magnitude of the force acting on the wire: (i) doubling the current through the wire; (ii) reversing the direction of the current; (iii) replacing the magnets with weaker ones.

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

> A current-carrying wire is positioned at right angles to a uniform magnetic field and experiences a force due to the motor effect.

## Mark scheme (4 marks)

1. (i) Doubling the current increases the magnitude of the force (the force doubles / the force increases).
2. (ii) Reversing the current reverses the direction of the force / the force acts in the opposite direction; the magnitude of the force is unchanged.
3. (iii) Using weaker magnets decreases the magnitude of the force (the force decreases / the force is smaller).
4. Correct reasoning linked to either (i) or (iii): the magnitude of the force depends on / is proportional to the magnitude of the current OR the strength of the magnetic field.

## Key terms

- [magnetic field](https://www.gradenine.co.uk/glossary/magnetic-field)
- [current](https://www.gradenine.co.uk/glossary/current)
- [force](https://www.gradenine.co.uk/glossary/force)

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](https://www.gradenine.co.uk/learn)
- [How to answer "State" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-places-a-straight-wire-ac5ca31f) · Published by Druglandscape Ltd.