A plotting compass is held close to a bar magnet and in line with its long axis. The magnet is turned end-for-end about its centre without moving the compass. The compass needle turns through half a turn and settles again.
Which explanation is correct?
The compass needle is demagnetised by the turn, then becomes an induced magnet with its poles exchanged.
The magnetic field at the compass becomes stronger, so the needle turns to display the increased field strength.
The magnetic field at the compass reverses direction, so the needle turns to align with the new field direction.
Both ends of the compass needle are attracted to the nearer pole, so the needle rotates as the magnet is turned.
70 exam-style questions on Edexcel GCSE Physics 12.1 Magnets and magnetic fields, covering 12.1.1 Magnetic poles, 12.1.2 Magnetic materials; permanent and induced magnets, 12.1.3 Magnetic fields, and 12.1.4 Plotting compasses and the Earth's magnetic field. Each one has a worked solution and a mark scheme showing where the marks go.