# A metal rod rests on two parallel conducting rails that are connected to a galvanometer. The rod is pushed along the rails so that it moves at a steady speed through a uniform magnetic field directed vertically downward. The galvanometer shows a steady deflection. The rod is then pushed at a greater speed through the same magnetic field. Explain what happens to the induced EMF when the speed is increased, and describe two other changes a student could make to the setup to increase the induced EMF further.

> Eduqas A-Level Physics — 4.5 Electromagnetic induction · Explain · 5 marks

> A metal rod is placed on two horizontal conducting rails connected to a galvanometer. The rod can slide freely along the rails. A uniform magnetic field is directed vertically downward through the region between the rails.

## Mark scheme (5 marks)

1. Increasing the speed increases the rate at which the rod cuts through magnetic field lines
2. A greater rate of cutting field lines produces a greater induced EMF
3. Use a stronger magnet / increase the strength of the magnetic field
4. Use a longer rod (increase the length of the conductor in the magnetic field)
5. Any second valid change: wrap the conductor into a coil with more turns / use a coil instead of a single rod (accept: increase number of turns in coil)

## Key terms

- [induced EMF](https://www.gradenine.co.uk/glossary/induced-emf)
- [magnetic field](https://www.gradenine.co.uk/glossary/magnetic-field)

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" 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-metal-rod-rests-on-two-17ec42a7) · Published by Druglandscape Ltd.