A student is given three physically identical metal bars, labelled X, Y, and Z. Two of these bars are magnetised (permanent magnets) and one is unmagnetised.
Describe and explain how the student can determine which of the three bars is the unmagnetised one, using only the three bars themselves.
(i) A step-down transformer is connected to a 120 V120\text{ V}120 V AC mains supply. The output power delivered by the secondary coil of the transformer is 30 W30\text{ W}30 W. The transformer is 100%100\%100% efficient.
Calculate the input current to the primary coil of the transformer.
(ii) Describe the main components of this step-down transformer by stating:
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.