Topic 6 - Electric Motors and Loudspeakers

Question 1

what 4 factors speed up a DC motor?

Answer 1

1. more current
2. more turns on the coil
3. stronger magnetic field
4. a soft iron core in the coil

Question 2

why does the coil in an electric motor rotate?

Answer 2

forces act on the two side arms of the coil, one up one down

Question 3

what does the split-ring commutator in a DC motor do?

Answer 3

swaps the electrical contacts every half turn so the motor rotates in the same direction

Question 4

how can the direction of a DC electric motor be reversed?

Answer 4

swapping the polarity of the DC supply or swapping the magnetic poles over

Question 5

how do loudspeakers work?

Answer 5

1. ac electrical signals from an amplifier are fed to a coil of wire in the speaker, which is wrapped around the base of a cone
2. the coil is surrounded by a permanent magnet, so the ac signals cause a force on the coil and make it move back and forth
3. this makes the cone vibrate, creating sounds