#P4.2a
describe how a magnet and a current-carrying conductor exert a force on one another
#P4.2b
show that Fleming’s left-hand rule represents the relative orientations of the force, the current and the magnetic field
#P4.2c
apply the equation that links the force on a conductor to the magnetic flux density, the current and the length of conductor to calculate the forces involved
#P4.2d
explain how the force exerted from a magnet and a current-carrying conductor is used to cause rotation in electric motors
an understanding of how electric motors work but knowledge of the structure of a motor is not expected
#P4.2e
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, generating a magnetic field that would oppose the original change
#P4.2f
explain how this effect is used in an alternator to generate a.c., and in a dynamo to generate d.c.
#P4.2g
explain how the effect of an alternating current in one circuit, in inducing a current in another, is used in transformers
#P4.2h
explain how the ratio of the potential differences across the two circuits in a transformer depends on the ratio of the numbers of turns in each
#P4.2i
apply the equations linking the potential differences and numbers of turns in the two coils of a transformer
#P4.2j
explain the action of the microphone in converting the pressure variations in sound waves into variations in current in electrical circuits, and the reverse effect as used in loudspeakers and headphones
an understanding of how dynamic microphones work using electromagnetic induction