# A diode is connected in a circuit with a battery and an ammeter. Explain what happens to the current measured by the ammeter when the diode is connected in the forward direction and then reversed so that it is connected in the reverse direction.

> OCR A-Level Physics A (H556) — 3.4 Materials · Explain · 5 marks

> A student is investigating how a diode controls the flow of current in a circuit. The student connects a diode in series with a battery and an ammeter, first in the forward direction, then turns the diode around so it faces the reverse direction.

## Mark scheme (5 marks)

1. In the forward direction, current flows (freely) through the diode
2. The ammeter shows a (measurable / significant) current reading when the diode is in the forward direction
3. In the reverse direction, the diode has a very large (high) resistance
4. In the reverse direction, (almost) no current flows through the diode
5. The ammeter reads (close to) zero when the diode is reversed, because the diode only allows current to flow in one direction

## Key terms

- [diode](https://www.gradenine.co.uk/glossary/diode)
- [current](https://www.gradenine.co.uk/glossary/current)
- [forward direction](https://www.gradenine.co.uk/glossary/forward-direction)
- [reverse direction](https://www.gradenine.co.uk/glossary/reverse-direction)
- [ammeter](https://www.gradenine.co.uk/glossary/ammeter)

## Related

- [Revision notes for OCR A-Level Physics A (H556)](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-diode-is-connected-in-a-3d770225) · Published by Druglandscape Ltd.