A student investigates how the electric force on a small charged ball depends on its distance from a charged metal dome.
The ball hangs from a long insulating thread. The student measures the electric force on the ball at different distances from the centre of the dome.
The Table shows the results.
Table
| Distance from centre of dome in cm\text{cm}cm | Electric force on ball in mN\text{mN}mN |
|---|---|
| 10 | 3.6 |
| 20 | 0.90 |
| 30 | 0.40 |
| 40 | 0.23 |
Describe how the electric force on the ball changes as the distance from the dome increases.
Explain the results.
Use the idea of an electric field in your answer.
The student says:
'The electric force is inversely proportional to the distance from the centre of the dome.'
Evaluate the student's statement.
Use data from the Table.
The student moves the ball to each new distance by holding the thread, and does not touch the ball.
Suggest why the ball must not be touched with a hand during the investigation.
80 exam-style questions on Edexcel GCSE Physics 11.2 Uses, dangers and electric fields, covering 11.2.1 Uses of electrostatic charge, 11.2.2 Dangers of sparking, 11.2.3 Electric fields, and 11.2.4 Electric fields and static electricity. Each one has a worked solution and a mark scheme showing where the marks go.