The primary coil of a transformer is connected to a battery and a switch. A voltmeter is connected across the secondary coil.
When the switch is closed, the voltmeter needle moves for a moment and then returns to zero.
Which statement explains this?
The magnetic field in the core changes only while the current is starting to flow
The battery supplies a current for only an instant, and then the current stops
The core becomes fully magnetised, so it blocks the field from the secondary coil
The secondary coil heats up quickly, so its resistance becomes far too large
48 exam-style questions on OCR GCSE Physics 4.2 Uses of magnetism, covering 4.2.1 The motor effect, 4.2.2 Fleming's left-hand rule, 4.2.3 The force on a current-carrying conductor, 4.2.4 The electric motor, 4.2.5 Electromagnetic induction, 4.2.6 Alternators and dynamos, 4.2.7 How transformers work, 4.2.8 Transformer turns ratio, 4.2.9 Potential differences and turns in transformers, and 4.2.10 Microphones, loudspeakers and headphones. Each one has a worked solution and a mark scheme showing where the marks go.