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(a) State Lenz’s Law of electromagnetic induction.
(b) Figure 13 shows a simple microphone in which sound waves from the person talking cause the cardboard diaphragm to vibrate.
(i) Explain how a varying current is induced in the coil when the diaphragm vibrates.
(ii) State two ways in which the induced current in (i) above can be increased.
(c) A transformer with 1200 turns in the primary circuit and 120 turns in the secondary circuit has its primary circuit connected to a 400V a.c source. It is found that when a heater is connected to the secondary circuit, it produces heat at the rate of 600w. Assuming 100% efficiency, determine the:
(i) Voltage in the secondary circuit.
(ii) Current in the primary circuit.
(iii) Current in the secondary circuit.