A technician tests a model conveyor system. An insulating rubber belt passes over an insulating nylon pad.
For each test, the belt and the pad are initially neutral. The technician passes the belt over the pad and then measures the charge on the belt immediately. Each test is repeated three times.
| Number of passes | Charge on belt in nC\text{nC}nC, test 1 | Charge on belt in nC\text{nC}nC, test 2 | Charge on belt in nC\text{nC}nC, test 3 |
|---|---|---|---|
| 6 | -3 | -4 | -5 |
| 12 | -7 | -8 | -9 |
| 18 | -11 | -12 | -13 |
| 24 | -15 | -16 | -17 |
| 30 | -19 | -31 | -21 |
Predict the mean charge on the belt after 42 passes.
Explain how the results support your prediction.
Explain what the negative readings show about the transfer of charge between the belt and the pad.
Before taking one of the readings, the technician touches the charged area of the belt with a bare hand.
Suggest how this affects the reading.
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.