Electrical power is produced in a power station by an alternating current (a.c.) generator. The output of the generator has a voltage of 15 000 V15\,000\text{ V}15000 V. The electrical power is transmitted at a voltage of 275 000 V275\,000\text{ V}275000 V.
Explain why electrical power is transmitted at a voltage of 275 000 V275\,000\text{ V}275000 V and not 15 000 V15\,000\text{ V}15000 V.
A laptop charger contains a transformer.
The input voltage to the transformer is 240 V240\text{ V}240 V. The output voltage from the transformer is 16 V16\text{ V}16 V and the output current is 3.0 A3.0\text{ A}3.0 A.
The efficiency of the transformer is 80%80\%80%.
Calculate the input current to the transformer.
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.