Three insulating strips P, Q and R are isolated from their surroundings. The table shows their charges before stage 1. The two successive rubbing stages use the same strips, without resetting their charges. In each stage, the stated negative charge is carried by electrons transferred in the direction shown.
| Strip | Charge before stage 1 |
|---|---|
| P | +7 nC+7\ \mathrm{nC}+7 nC |
| Q | −2 nC-2\ \mathrm{nC}−2 nC |
| R | −1 nC-1\ \mathrm{nC}−1 nC |
| Stage | Direction of electron transfer | Charge carried by the transferred electrons |
|---|---|---|
| 1 | P to Q | −5 nC-5\ \mathrm{nC}−5 nC |
| 2 | R to P | −3 nC-3\ \mathrm{nC}−3 nC |
Calculate the charge on each strip after both stages and the total charge of the three strips.
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.