recall that a change in the magnetic field around a conductor can give rise to an induced potential difference across its ends, which could drive a current

explain the action of a moving coil microphone in converting the pressure variations in sound waves into variations in current in electrical circuits

recall that the direction of the induced potential difference drives a current which generates a second magnetic field that would oppose the original change in field

use ideas about electromagnetic induction to explain a potential difference/time graph showing the output from an alternator being used to generate a.c.

explain how an alternator can be adapted to produce a dynamo to generate d.c., including explaining a potential difference/time graph

explain how the effect of an alternating current in one circuit in inducing a current in another is used in transformers

describe how the ratio of the potential differences across the two circuits of a transformer depends on the ratio of the numbers of turns in each

apply the equations linking the potential differences and numbers of turns in the two coils of a transformer, to the currents and the power transfer involved and relate these to the advantages of power transmission at high voltages:

a) potential difference across primary coil × current in primary coil = potential difference across secondary coil × current in secondary coil

b) potential difference across primary coil ÷ potential difference across secondary coil = number of turns in primary coil ÷ number of turns in secondary coil