Which of the following pairs correctly identifies the best material for each component of an efficient electrical transformer and the primary reason for its choice?
Core: Soft iron to minimize hysteresis loss; Windings: Copper to minimize Joule heating (I2RI^2RI2R loss).
Core: Steel to maintain a permanent magnetic field; Windings: Copper to maximize magnetic flux leakage.
Core: Copper to ensure high electrical conductivity through the center; Windings: Soft iron to restrict current flow.
Core: Soft iron to act as an electrical insulator; Windings: Steel to increase the mechanical strength of the coils.
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.