7. Electricity & Magnetism

Question 1

What is a magnetic field?

Answer 1

A region of space where magnetic material can experience a force

Question 2

What type of poles attract?

Answer 2

Unlike poles

Question 3

What type of poles repel?

Answer 3

Like poles

Question 4

What is inside a compass?

Answer 4

A tiny bar magnet

Question 5

How does a compass show that the earth generates its own magnetic field?

Answer 5

When the compasses are not near a magnet they point north

Question 6

Which direction do field lines point in?

Answer 6

North to South

Question 7

What does it mean when field lines are closer together?

Answer 7

They are stronger

Question 8

Do field lines ever touch or cross?

Answer 8

No

Question 9

Where is the magnetic field strongest?

Answer 9

At the poles of the magnet

Question 10

What do the direction of the field lines show?

Answer 10

The direction of the force that would act on a tiny N-pole placed at that point

Question 11

What are magnetic materials made of?

Answer 11

Molecular magnets

Question 12

What are molecular magnets?

Answer 12

Tiny magnets with N and S poles

Question 13

What are domains?

Answer 13

Groups of molecular magnets

Question 14

How are the molecular magnets when a material is unmagnetised?

Answer 14

The unmagnetised domains point in random directions

Question 15

How are the molecular magnets when a material is magnetised?

Answer 15

Most molecular magnets are aligned

Question 16

What does saturated mean when talking about a magnet?

Answer 16

When all molecular magnets are aligned

Question 17

What happens when a magnet breaks?

Answer 17

Two magnets are simply made

Question 18

Is iron a soft or hard magnetic material?

Answer 18

Soft

Question 19

What are the properties of a soft magnetic material?

Answer 19

• easy to magnetise

* will demagnetise easily (so useful in electromagnets)

Question 20

What type of magnetic material is used for electromagnets?

Answer 20

Soft

Question 21

Why is soft magnetic material used in electromagnets?

Answer 21

It is easy to magnetise and demagnetise

Question 22

Is steel a hard or soft magnetic material?

Answer 22

Hard

Question 23

What are the properties of a hard magnetic material?

Answer 23

• harder to magnetise

* also hard to demagnetise

Question 24

What is hard magnetic material used for?

Answer 24

Permanent magnets e.g. needles in compasses

Question 25

What is an electromagnet?

Answer 25

A solenoid with an iron core inside

Question 26

What is a solenoid?

Answer 26

A coil of wire

Question 27

What happens when a current is passed along the wire in an electromagnet?

Answer 27

A magnetic field is created and as a result the iron core is magnetised

Question 28

What happens in an electromagnet when the current is switched off?

Answer 28

The iron bar loses it’s magnetism because it’s a temporary magnet

Question 29

What can the strength of the magnetic field in an electromagnet be increased by?

Answer 29

• increasing the voltage or decreasing the resistance - to INCREASE THE CURRENT
• increasing the number of turns on the coil
• inserting an iron core

Question 30

Where are electromagnets used?

Answer 30

• cranes

* in hospitals dealing with eye injuries - remove steel splinters

Question 31

How does an electric bell work?

Answer 31

• bell-push completes circuit and current flows through electromagnet
• iron is attracted towards electromagnet and hammer hits gong
• movement breaks circuit so current stops and electromagnet is switched off
• spring pulls iron back so contact is made and sequence repeats

Question 32

When will a wire NOT experience a force when placed in a magnetic field?

Answer 32

If it’s parallel to the direction of the field