Magnetism

Question 1

How do microphones work?

Answer 1

1. Soundwaves hit a diaphragm connected to a coil wrapped around a magnet
2. This causes the coil to move in a magnetic field, inducing a current
3. Louder sound waves move the coil more inducing more PD & current

Question 2

What affects the size of PD induced by the generator effect?

Answer 2

1. Stronger magnetic field
2. Move wire quicker
3. Shape wire into a coil

Question 3

How do alternators work?

Answer 3

1. Generators rotate a coil in a magnetic field
2. Direct current induced which changes direction every half turn
3. Slip rings and brushes prevent this and turn it into an alternating current

Question 4

What are dynamos?

Answer 4

Direct current generators with slip ring commutators which makes current keep changing direction

Question 5

What is an induced magnet?

Answer 5

A material which becomes magnet when introduced to a magnetic field

Question 6

What is the motor effect?

Answer 6

When a current-carrying wire is put between two poles, the magnetic field of the wire intercepts the magnetic field from the magnet, exerting force, moving the wire

Question 7

How can a magnetic field be reversed?

Answer 7

1. Current flow opposite way
2. Swap the magnetic poles

Question 8

What impacts the size of force induced by motor effect?

Answer 8

1. Magnetic flux density
2. Size of current in wire
3. Length of wire

Question 9

How does a DC motor work?

Answer 9

1. Forces act on the side arms of a current carrying coil
2. The coil rotates on a spindle
3. The split ring commutator keeps swapping contacts, so the motor continues the same way

Question 10

What is an electromagnet?

Answer 10

A solenoid with an induced iron core which can have its magnetic field turned on and off with a current

Question 11

Equation for force produced by motor effect?

Answer 11

Force = Flux density x current x length