9.01 Magnets

Question 1

Where does a magnetic force come from in a magnet?

Answer 1

The 2 poles.

Question 2

What are the names of the 2 poles?

Answer 2

North-seeking pole (N pole)

South-seeking pole (S pole)

Question 3

What happens to a bar magnet if it is suspended from a rope free to move?

Answer 3

It swings around until it lies roughly north-south. This is used to name the 2 poles of a magnets

Question 4

Like forces ______, Unlike forces _______

Answer 4

Repel

Attract

Question 5

The closer the poles, the ______ the force between them.

Answer 5

Greater

Question 6

What are the properties of a magnet?

Answer 6

1. Has a magnetic field around it
2. Has 2 opposite poles, which exert forces on other magnets.
3. Will attract magnetic materials by inducing magnetism in them. Some materials become permanently magnetized (steel), while others temporary (iron)
4. Will exert little/no force on non- magnetic material

Question 7

What is induced Magnetism?

Answer 7

Since materials like iron/steel can be magnetized by a magnet, they will be attracted to the magnet.

Therefore the magnet induced magnetism in them.

The induced pole near the magnet is the opposite of the pole at the end of the magnet.

Question 8

Describe how steel is a permanent magnet.

Answer 8

After induced magnetism when the steel is pulled away from the magnet, it still keeps some of its induced current and becomes a permanent magnet.

Question 9

Describe how iron is a temporary magnet.

Answer 9

When the iron is pulled away from the magnet it loses virtually all of its induced magnetism.so it is only a temporary magnet.

Question 10

How can you make a magnet?

Answer 10

A piece of steel becomes permanently magnetized when placed near a magnet (Since the ‘atomic magnets’ (electrons) line up with each other. BUT magnetism caused by placing next to a magnet is usually weak, SO to get stronger magnetism.
Together billions of electrons (tiny atomic magnets act as one big magnet)

1. STROKE the metal by one end of another magnet (a strong magnet).
2. The most effective way of magnetizing is to place the metal in a long coil of wire and passing a dc current in the coil. (The current has a magnetic effect which magnetizes the steel)

Question 11

What is a magnetic material?

Answer 11

A material which can be magnetized and is attracted to magnets .

All strongly magnetic materials contain iron, nickel, cobalt. Ex (steel is mainly iron)

Question 12

What are strongly magnetic metals called?

Answer 12

Ferromagnetics

They can be hard or soft depending on how well the keep their magnetism after being magnetized

Question 13

What is ferrous and non-ferrous?

Answer 13

Ferrous is iron and alloys containing iron

Non ferrous contain Aluminum, Copper and other non- magnetic metals

Question 14

What are hard magnetic materials?

Answer 14

Steel, Alcomax and Magnadut are hard magnetic materials

They are hard (difficult) to magnetize but will keep their magnetism (will not readily lose it)

PERMANENT

Question 15

What are soft Magnetic materials?

Answer 15

Iron, mumetal

Are easy to magnetize, and lose magnetism easily, since their magnetism is temporary.

They are used in cores of electromagnets and transformers because the magnetic effect can be controlled ‘switched’ on and off or reversed easily.

Question 16

What are non magnetic materials?

Answer 16

Brass, copper, zinc, tin and aluminum, and the non-metals.

Question 17

How do you demagnetize a metal that has been magnetized?

Answer 17

1. You put it in a long coil of wire and pass an ALTERNATING current (not DC) so that the atomic magnets (electrons) point at random directions.
2. Heat the magnetized metal to a high temp so that the atomic magnets are thrown of line.
3. Hammer the magnetized metal so that the atomic magnets are thrown of line.