A student investigates how the charge on a polythene rod depends on the number of times the rod is rubbed with a cloth.
The student uses a coulombmeter to measure the charge on the rod.
The Table shows the results.
Table
| Number of rubs | Charge on rod in nC\text{nC}nC |
|---|---|
| 5 | -4 |
| 10 | -8 |
| 15 | -15 |
| 20 | -16 |
| 25 | -20 |
Identify the anomalous result.
Describe the relationship between the number of rubs and the size of the charge on the rod.
Predict the charge on the rod after 30 rubs.
Give the charge on the cloth after 20 rubs.
Explain your answer.
The student repeats the investigation using a damp cloth.
The rod gains much less charge.
Suggest why.
91 exam-style questions on Edexcel GCSE Physics 11.1 Charging by friction, covering 11.1.1 Charging insulators by friction, 11.1.2 Forces between charges, 11.1.3 Electrostatic phenomena, and 11.1.4 Earthing and removing charge. Each one has a worked solution and a mark scheme showing where the marks go.