Induced Magnetism,

Question 1

How can you use iron filings to see the field lines?

Answer 1

1) Place the magnet under a piece of card.
2) Sprinkle iron filings over the piece of card.
3) Tap the piece of card - this will cause the iron filings to accumulate along the field lines.

Question 2

How can you use a compass to draw field lines?

Answer 2

1. Place the plotting compass near the magnet on a piece of paper.
2. Mark the direction the compass needle points.
3. Move the plotting compass to many different positions in the magnetic field, marking the needle direction each time.
4. Join the points to show the field lines.

Question 3

What three materials are magnets?

Answer 3

Iron/Nickel/Cobalt.

Question 4

Define “magnetically hard” and give an example.

Answer 4

Lose their magnetism slowly- domains stay aligned for longer- steel.

Question 5

Define “magnetically soft” and give an example.

Answer 5

Lose their magnetism really quickly- domains quickly return to original position- magnetically soft,

Question 6

Define “permanent magnet” and “induced magnet” and compare.

Answer 6

Permanent magnets are magnets that produce their own magnetic field, whereas induced magnets are magnets that only have a temporary magnetic field.

Question 7

Field lines go in from where to where, and from where to where?

Answer 7

Field lines go in from South to North.
The field lines go from North to South.

Question 8

Define “magnetic materials”.

Answer 8

Any object that can be influenced by magnetic fields and has the potential to become a magnet.

Question 9

How can you tell the Earth’s core is magnetic?

Answer 9

A magnetic compass contains a small bar magnet. The needle of the compass points in the direction of the Earth’s magnetic field.
This shows that the core is magnetic.

Question 10

What force is between an induced magnet and a permanent magnet?

Answer 10

A magnetic material will temporarily become a magnet when it is close to a permanent magnet. There is always an attractive force between an induced magnet (or magnetic material) and a permanent magnet.

Question 11

Name 4 key points about magnetism.

Answer 11

• Magnetic materials can be attracted by a magnet, but can’t be repelled by a magnet.
• Only two magnets can repel each other.
• Non-magnetic materials will never be attracted to magnets.
• Permanent magnets are always magnetic, even when they are not near other magnets.

Question 12

Describe the poles in induced magnets.

Answer 12

The permanent magnet induces (creates) temporary poles in the magnetic material and these align so that the magnetic material is attracted to the permanent magnet.

If the north pole of the magnet is next to the magnetic material, then a south pole will be induced in the part of the material closest to the magnet.

Question 13

What are the domains like in permanent magnets, induced magnets and non-magnetic materials?

Answer 13

Permanent Magnets-
Domains are all lined up.

Induced-
More have been lined up in one direction due to the magnetic field of the permanent magnet it is near to.

Non-magnetic Material-
Random.

Question 14

The number of field lines passing through a particular area is called ….

Answer 14

Magnetic flux density/magnetic field strength.

Question 15

Magnets move in what direction?

Answer 15

The direction that makes the fields line shorten. The density of the field lines shows you the strength of the field.

Question 16

How can you tell the Earth’s core behaves like a bar magnet?

Answer 16

If a compass is mounted vertically (a dipping compass), it shows that the Earth’s magnetic field enters the Earth at different angles in different places. Therefore, it acts like a bar magnet.

Scientists are not sure what causes the field. It could be produced by convection currents in the molten iron core of the Earth.

Question 17

Why is the North Pole called a South Pole, and vice versa?

Answer 17

The Earth’s South Pole is the magnetic North Pole, and vice versa. It’s called the North Pole because the North Pole of the compass points to it- however, that still means it’s a south Pole because opposite sides attract.

Question 18

Define “magnetic field lines”.

Answer 18

Magnetic field lines are lines drawn to represent the strength and direction of a magnetic field. The arrows on magnetic field lines show the direction of a magnetic
field. The arrows always point from the north pole of the magnet to the south pole. The strength of the magnetic field at any point is indicated by the density of the field lines at that point.

Question 19

Why must compasses be weighted?

Answer 19

They need to be weighted because the Earth’s magnetic field is like that of a bar magnet.

Question 20

What are the problems of using a compass in space?

Answer 20

If you were trying to navigate with a compass in space, just remember that compass is going to respond to the strongest and closest magnetic field. It will point north, north to the pole of the planet and the bar magnet in the compass will be attracted to the magnetic South Pole. If on the moon, the magnet field is not polarised, so the compass would respond to a different magnetic field, and therefore the direction for the astronaut would be incorrect.

Question 21

How does a compass behave when alone?

Answer 21

Earth has a magnetic field; if the compass is not near any other magnetic fields it should align with the magnetic field of Earth. The compass needle is marked so that you can tell which end of the needle is pointing toward the “North Pole”/magnetic South Pole of the planet. This will allow you to find out which direction is where,