A separator uses a permanent bar magnet outside a non-magnetic chute to remove iron fragments from material passing through the chute. The magnet does not touch the iron fragments.
The same magnet was tested in four arrangements.
| Arrangement | Part of the magnet closest to the iron fragment | Distance between the magnet and the iron fragment in mm | Force on the iron fragment in N |
|---|---|---|---|
| P | midpoint | 2 | 0.90 |
| Q | pole | 2 | 2.40 |
| R | pole | 5 | 1.20 |
| S | pole | 8 | 0.60 |
The force on an iron fragment must be at least 1.00 N for the separator to remove it.
Compare the force in arrangement P with the force in arrangement Q. Explain the difference.
Arrangement R is chosen. During use, a layer of non-magnetic material builds up between the chute wall and the iron fragments. This increases the distance between the magnet and the fragments from 5 mm to 8 mm.
Explain whether the separator will still remove the iron fragments.
80 exam-style questions on AQA GCSE Physics 7.1 Permanent and induced magnetism, magnetic forces and fields, covering 7.1.1 Poles of a magnet and 7.1.2 Magnetic fields. Each one has a worked solution and a mark scheme showing where the marks go.