a.[4]
Explain two similarities and two differences between the operation of a moving-coil loudspeaker and a moving-coil microphone.
b.[3]
The diagram shows a straight horizontal wire positioned in the gap between the North pole (on top) and the South pole (on bottom) of a permanent magnet.
Describe and explain the direction of the force acting on the wire when the switch is closed.
c.[3]
A current of 6.4 A6.4\text{ A}6.4 A passes through a wire with a length of 0.75 m0.75\text{ m}0.75 m.
The wire is in a magnetic field of magnetic flux density 0.55 T0.55\text{ T}0.55 T.
Calculate the force acting on the wire.
Give your answer to 2 significant figures.