# Explain why two identical resistors connected in parallel have a combined resistance that is less than the resistance of either individual resistor, using a model of current flow through conducting materials.

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

## Mark scheme (4 marks)

1. In a conducting material, current is carried by free (conduction) electrons moving through the material in response to an electric field / potential difference.
2. Connecting resistors in parallel provides additional pathways (cross-sectional area through which electrons can flow is effectively increased).
3. For the same applied potential difference, the total current drawn from the source is greater than through a single resistor alone, because each resistor independently carries its own current.
4. Since resistance R = V/I, a larger total current for the same voltage gives a smaller combined resistance, which is therefore less than either individual resistor's resistance.

## Key terms

- [resistance](https://www.gradenine.co.uk/glossary/resistance)

## Related

- [Revision notes for IB DP Physics Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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