Two students investigate how the electrical resistance of a wire depends on its length. They tape a length of resistance wire to a metre ruler and connect it to a digital multimeter set to measure resistance using crocodile clips.
Look at their results:
| Length of wire (cm) | Resistance Attempt 1 (Ω\OmegaΩ) | Resistance Attempt 2 (Ω\OmegaΩ) | Resistance Attempt 3 (Ω\OmegaΩ) | Mean Resistance (Ω\OmegaΩ) |
|---|---|---|---|---|
| 20 | 5.4 | 5.1 | 5.3 | 5.267 |
| 40 | 10.6 | 10.5 | 10.8 | 10.8 |
| 60 | 15.9 | 16.2 | 11.2 | 16.1 |
| 80 | 21.3 | 21.5 | 21.4 | 21.4 |
Describe the pattern shown by these results. Use data in your answer.
The students made two mistakes when they recorded their results and completed the table. Identify the mistakes and explain what they should have done.
The students have correctly handled an error in their results. Identify the error and explain how it was correctly handled.
The students plan to plot a graph of mean resistance against length. What would you expect a graph of these results to look like?
The actual mean resistance values are more than expected. Suggest two possible experimental faults with the setup.
For one of the faults identified in (b)(i), suggest how the experimental procedure could be improved.
47 exam-style questions on OCR GCSE Physics Practical skills. Each one has a worked solution and a mark scheme showing where the marks go.