# A student connects two resistors in parallel with each other, and this parallel combination is connected in series with a battery and an ammeter. The student measures the current from the battery. She then removes one of the resistors from the parallel combination, leaving only a single resistor connected in series with the battery and ammeter. Explain what happens to the current reading on the ammeter and the voltage across the remaining resistor when one resistor is removed.

> Eduqas A-Level Physics — 2.2 DC circuits · Explain · 5 marks

> A student is investigating how the arrangement of resistors in a circuit affects current and voltage.

## Mark scheme (5 marks)

1. Removing one resistor reduces the number of parallel paths, so the total resistance of the circuit increases.
2. Because the battery voltage (e.m.f.) stays the same / is constant, a higher resistance means the total current from the battery decreases.
3. The ammeter reading decreases (the current falls).
4. The full battery voltage now acts across the single remaining resistor (voltage across it increases).
5. In the original parallel combination both resistors shared the same voltage (equal to the battery voltage), whereas in the new series-only circuit there is no voltage drop elsewhere, so the remaining resistor has a higher voltage across it than before / the same as the supply.

## Key terms

- [current](https://www.gradenine.co.uk/glossary/current)
- [voltage](https://www.gradenine.co.uk/glossary/voltage)
- [ammeter](https://www.gradenine.co.uk/glossary/ammeter)

## 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-student-connects-two-resistors-in-0e8f05c2) · Published by Druglandscape Ltd.