# Explain why the current through a resistor connected in a circuit increases when the potential difference across it is increased, using a model of charge carriers.

> IB DP Physics Standard Level (2023 syllabus) — B.5 Current and circuits · Explain · 4 marks

> A simple circuit consists of a battery connected to a single resistor. The battery is replaced by one of greater electromotive force (emf), causing the current in the circuit to increase.

## Mark scheme (4 marks)

1. The battery (source of emf) acts as an energy source that does work on charge carriers, giving them energy / creating an electric field that drives charge carriers through the resistor.
2. A greater potential difference means more energy is transferred per unit charge / a stronger electric field acts on the charge carriers.
3. The charge carriers (electrons) therefore move with greater drift velocity / are accelerated more strongly through the resistor.
4. A greater drift velocity means more charge passes a given cross-section per unit time, so the current (defined as rate of flow of charge) is greater.

## Key terms

- [potential difference](https://www.gradenine.co.uk/glossary/potential-difference)
- [current](https://www.gradenine.co.uk/glossary/current)
- [charge carrier](https://www.gradenine.co.uk/glossary/charge-carrier)

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-current-through-a-9fdc26d0) · Published by Druglandscape Ltd.