An exercise machine drives a small alternator. At its present rotation rate, the alternator produces a peak potential difference of 5.0 V at a frequency of 18 Hz. The peak potential difference is directly proportional to the rotation rate.
The rotation rate is changed so that the alternator produces a peak potential difference of 15 V. Nothing else is changed.
Which statement describes the change and the new output frequency?
The rotation rate is doubled and the frequency becomes 36 Hz36\ \mathrm{Hz}36 Hz.
The rotation rate is tripled and the frequency becomes 54 Hz54\ \mathrm{Hz}54 Hz.
The rotation rate is tripled and the frequency stays at 18 Hz18\ \mathrm{Hz}18 Hz.
The rotation rate is tripled and the frequency becomes 6 Hz6\ \mathrm{Hz}6 Hz.
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.