TOPIC 7: Magnetism

Question 1

What is magnetism?

Answer 1

The ability of magnets to attract and repel other magnets without touching them

Question 2

Attraction:

Answer 2

• the south pole is attracted to the north pole of a magnet (unlike charges attract)
• a non-contact force

Question 3

Repulsion:

Answer 3

• like charges repel
• non-contact force

Question 4

What are the magnetic materials?

Answer 4

• Iron
• Nickel
• Cobalt

Question 5

Properties of magnetic materials:

Answer 5

• they don’t always act as magnets
• ## can be attracted to a magnet, but cannot be repelled (only two magnets can repel each other)

Question 6

What is induced magnetism?

Answer 6

• A permanent magnet produces its own magnetic field
• An induced magnet is a material that becomes a magnet when it is placed in a magnetic field
• Induced magnetism always causes a force of attraction
• When removed from the magnetic field an induced magnet loses most/all of its magnetism quickly.

Question 7

What is a magnetic field?

Answer 7

A magnetic field is the area around a magnet where another magnet or magnetic material feels a force. When the magnetic fields of two magnets overlap, the fields cause them to attract or repel each other.

Question 8

What does the strength of a magnetic field depend on?

Answer 8

• the distance from the magnet/ the magnetic field is strongest at the magnet’s poles
• the size of the current
• in a diagram, the closer the lines are, the stronger the magnetic field

Question 9

Magnetic compass:

Answer 9

• contains a small bar magnet
• the needle of the compass points in the direction of the Earth’s magnetic field

Question 10

What do the arrows on the magnetic field lines show?

Answer 10

• the direction of the magnetic field
• the arrows always point from the north pole of the magnet to the south pole

Question 11

Left hand rule:

Answer 11

Thumb = force
First finger = magnetic field
Second finger = current

Question 12

Right hand rule:

Answer 12

Thumb = current
Curled fingers into palm = magnetic field

Question 13

What is a solenoid?

Answer 13

a loop of wire coiled into a cylindrical shape

Question 14

When is an electromagnet formed?

Answer 14

When a current carrying wire is wrapped around an iron core. The iron core increases the magnetic field strength of the solenoid.

Question 15

What is the cause of the motor effect?

Answer 15

The field created by the electric current interacts with the magnetic field that the wire is placed inside. This causes a force on the wire.

Question 16

Electric motors:

Answer 16

A coil carrying an electrical current will rotate in a magnetic field because the current going up one side of the coil is flowing in the opposite direction to the current coming back down the other side