A magnetic pickup tool contains a permanent magnet behind a protective cap. The tool is used to lift a steel screw from inside a machine. The screw touches the outside of the cap.
With a cap 4 mm thick, the screw sometimes falls off. The cap is replaced by one 1 mm thick.
Explain why the thinner cap makes the screw less likely to fall off the tool. Use ideas about the magnetic field in your answer.
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.