State two advantages that electromagnets have, compared with permanent magnets.
Select one option from each of the columns below to indicate the combination that would produce the strongest electromagnet.
| Column 1: Number of turns | Column 2: Core material | Column 3: Current |
|---|---|---|
| [ ] 1500 turns | [ ] Plastic | [ ] 4.5 A |
| [ ] 750 turns | [ ] Air | [ ] 3.0 A |
| [ ] 150 turns | [ ] Iron | [ ] 1.5 A |
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.