LONGER ANSWERS PAPER2

Question 1

how does a motor work? (4)

Answer 1

The sides of the coil experience a force in opposite directions
The forces cause moments that make the coil rotate in the same direction
Each half-turn the two halves of the commutator swap from one brush to the other
Each half-turn the commutator reverses the direction of the current

Question 2

how does an alternator work?

Answer 2

the coil cuts magnetic field lines
a potential difference is induced across the coil
there is a complete circuit, so a current is induced
the two ends of the coil stay in contact with the same brush
the direction of the (induced) current / potential difference reverses every half turn

Question 3

how does a dynamo work?

Answer 3

the coil cuts magnetic field lines
a potential difference is induced across the coil
there is a complete circuit, so a current is induced
each half-turn, the two ends of the coil swap from one brush to the other
the direction of the (induced) current / potential difference does not reverse every half turn

Question 4

describe how a microphone works

Answer 4

Sound waves strike diaphragm and move it backwards and forwards at same frequency as sound.
Moving diaphragm moves coil backwards and forwards.
Coil cuts through magnetic field of magnet which induces an alternating current at same frequency as sound.