A small-scale wind turbine rotates a rectangular coil within a magnetic field, acting as an alternating current (a.c.) generator.
The coil rotates with a constant frequency f=5 Hzf = 5\text{ Hz}f=5 Hz.
Calculate the period TTT of the alternating electromotive force (e.m.f.) produced.
The coil starts from a vertical position (where the magnetic flux linkage is maximum and the induced e.m.f. is zero). State the two values of time ttt within the first cycle (0≤t≤T0 \le t \le T0≤t≤T) at which the magnitude of the induced e.m.f. is at its maximum.
The wind speed increases, causing the coil to rotate at 10 Hz10\text{ Hz}10 Hz instead of 5 Hz5\text{ Hz}5 Hz. State two ways in which the induced e.m.f. changes.
The terminals of this generator are connected to the primary coil of a transformer. Explain how the alternating voltage in the primary coil induces an alternating e.m.f. in the secondary coil.
Explain, using appropriate physics relationships, why transmitting electrical power across transmission lines of resistance RRR at higher voltages results in lower power losses.
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.