A loudspeaker cone initially moves forwards when a current flows through its coil. The current is reversed and the permanent magnet is also reversed.
What is the direction of the force on the coil?
Backwards, because reversing both changes reverses the force direction.
Forwards, because reversing both changes leaves the force direction unchanged.
Zero, because the two reversals cancel the magnetic field completely.
Sideways, because the two reversals rotate the force through a right angle.
92 exam-style questions on Edexcel GCSE Physics 13.1 Inducing a current, covering 13.1.1 Producing an electric current by induction, 13.1.2 Factors affecting the induced potential difference, 13.1.3 Alternators and dynamos, and 13.1.4 Microphones and loudspeakers. Each one has a worked solution and a mark scheme showing where the marks go.