Electromagnetism

Question 1

What is a permanent magnet?

Answer 1

A magnet that produces its own magnetic field all of the time.

Question 2

What is an induced magnet?

Answer 2

A object that only becomes magnetic when placed inside a magnetic field.

Question 3

Explain the process of plotting magnetic fields.

Answer 3

1. Place compass at a point around a bar magnet.
2. Draw a dot where the compass points.
3. Move compass to this dot.
4. Repeat until a full field is drawn.

Question 4

What happens if an electrical current flows through a wire?

Answer 4

It produces a magnetic field around the wire

Question 5

(Electromagnet) What happens when the direction of the current is reversed?

Answer 5

The direction of the field is reversed

Question 6

What is a solenoid?

Answer 6

A coil of wire

Question 7

How do you increase the magnetic field produced by a wire?

Answer 7

By bending a wire into a solenoid

Question 8

What is the shape of a magnetic field around a solenoid similar to?

Answer 8

The magnetic field around a bar magnet

Question 9

Electric motor: why does the wire spin?

Answer 9

1. There is a force experienced on each side of the coil
2. The forces are in opposite directions so it spins

Question 10

Why do current-carrying wires experience a force inside a magnetic field?

Answer 10

The interaction between the field in the wire and the other magnetic field creates a force in the opposite direction.

Question 11

Motor effect: how can you reverse the direction of the force?

Answer 11

Reverse the current or direction of magnetic field

Question 12

What does the thumb represent in Fleming’s left hand rule?

Answer 12

Motion

Question 13

What does the first finger represent in Fleming’s left hand rule?

Answer 13

Field

Question 14

What does the second finger represent in Fleming’s left hand rule?

Answer 14

Current

Question 15

How do electric motors work? (4 steps)

Answer 15

1. There are magnetic fields from the permanent magnet and current in wire.
2. The current is in opposite directions at each side of the coil of wire.
3. So there is a force exerted - up on one side and down on the other.
4. A split-ring commutator reverses the current as the motor turns so there is an equal force on each side.

Question 16

How can an electric motor be made to spin faster?

Answer 16

By increasing the current in the coil or strength of magnetic field

Question 17

How can an electric motor be made to spin in the opposite direction?

Answer 17

By reversing the direction of the current or magnetic field

Question 19

How can you increase the strength of a magnetic field produced by a solenoid?

Answer 19

Putting an iron core inside of it

Question 20

What does the thumb represent in Fleming’s left-hand rule?

Answer 20

Motion

Question 21

What does the first finger represent in Fleming’s left-hand rule?

Answer 21

Field direction

Question 22

What does the second finger represent in Fleming’s left-hand rule?

Answer 22

Current direction

Question 23

What is magnetic flux density?

Answer 23

A measure of the strength of a magnetic field

Question 24

Explain the motor effect.