4.1 Simple phenomena of magnetism

Question 1

What causes magnetic forces? e.g between a magnet and ferrous metal.

Answer 1

The interaction of magnetic fields

Question 2

What is induced magnetism?

Answer 2

When a magnet attracts a ferrous metal it induces (creates) a magnetic field in it as the domains in the metal line up to make it a magnet

Question 3

Different methods of magnetisation

Answer 3

1. Running a d.c through the metal

2. Stroking with a magnetic with the North side about 10 times. The starting side becomes the North

Question 4

Different methods of demagnetisation

Answer 4

1. Hammering the magnet
2. Running an a.c through the magnet
3. Heating at high temperatures

Question 5

Describe an experiment to determine field lines of a magnet.

Answer 5

1. Put a magnet under a piece of paper

2. Sprinkle iron fillings on top of the paper.

Question 6

What are some magnetic properties of steel?

Answer 6

1. Magnetises slowly (low susceptibility)
2. Keeps magnetism for a long period of time (high retentivity)
3. Better used as a permanent magnet

Question 7

What are some magnetic properties of soft iron?

Answer 7

1. Magnetises fast (high susceptibility)
2. Loses magnetism fast (low retentivity)
3. Better for electromagnets and transformers

Question 8

Use of a permanent magnet

Answer 8

1. Useful when magnet is need for long periods of time.
2. Fridge door magnets
3. Compases
4. Loudspeaker

Question 9

Use of an electromagnet.

Answer 9

1. Useful when magnet needs to be turned off and on again

2. Scrapyard when you need to carry a car from one place to the other