A transformer has a primary coil and a secondary coil wound on a soft-iron core.
Identify the option for each row that best describes the magnetic field in the soft-iron core under the given condition.
| Primary coil current | Constantly changing magnetic field | Constant (steady) magnetic field | Zero magnetic field |
|---|---|---|---|
| Alternating current (a.c.) | |||
| Steady direct current (d.c.) |
State and explain the effect on the output voltage across the secondary coil of:
increasing the number of turns on the secondary coil (while keeping the primary coil input the same).
State and explain the effect on the output voltage across the secondary coil of:
replacing the soft-iron core with a non-magnetic plastic core.
275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.