A food factory transfers flour through a pipe into an enclosed steel hopper. Fine flour dust mixes with air inside the hopper.
The outside of the hopper is covered with paint, which is an electrical insulator. A technician tests two arrangements for connecting the hopper to Earth. The same mass of flour is transferred at the same flow rate in each test.
| arrangement | surface to which the earthing cable is connected | maximum charge measured on the hopper / µC |
|---|---|---|
| P | painted steel | 7.6 |
| R | bare steel exposed by removing some paint | 0.2 |
Explain which arrangement should be used to reduce the risk of an explosion. Use the information in the table.
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.