A moving-coil microphone produces an alternating signal. During part of each vibration the coil moves in one direction through the magnetic field, then moves back.
Which statement explains the change in signal polarity?
The resistance of the coil reverses, so the induced potential difference reverses.
The magnet loses its field, so the induced potential difference reverses.
The sound changes its speed, so the induced potential difference reverses.
The direction of motion reverses, so the induced potential difference reverses.
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.