In the construction of an efficient mains transformer, which choice correctly identifies the ideal materials for the coils and the core, along with the physical reason for their selection?
Coils: Copper (high electrical conductivity); Core: Soft iron (easily magnetized and demagnetized)
Coils: Soft iron (low electrical resistance); Core: Copper (easily magnetized and demagnetized)
Coils: Copper (low thermal conductivity); Core: Steel (retains permanent magnetism)
Coils: Aluminium (high magnetic permeability); Core: Soft iron (high electrical resistance)
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.