Which sequence describes how a transformer produces a potential difference across its secondary coil?
d.c. in primary coil →\rightarrow→ constant magnetic field in core →\rightarrow→ p.d. induced in secondary coil
a.c. in primary coil →\rightarrow→ current flows through the core →\rightarrow→ p.d. induced in secondary coil
a.c. in primary coil →\rightarrow→ changing magnetic field in core →\rightarrow→ p.d. induced in secondary coil
changing magnetic field in core →\rightarrow→ a.c. in primary coil →\rightarrow→ p.d. induced in secondary coil
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.