Magnets

What causes magnetism?

movement of electrons in an atom which makes a magnetic field

What is a domain?

a group of atoms that act as a magnet

How are the domains in non-magnetic material oriented?

• randomly

• magnetic fields cancel each other out

How are the domains in magnetic materials arranged when magnetised?

Align towards the magnet

What are magnetic metals?

Nickel

Iron

Cobalt

Why are permanent magnets made of steel?

It does not lose magnetism easily

How can an object made of steel be made to become a permanent magnet?

1. Stroke a steel object with a magnet using one pole in one direction

2. This will cause the domains of the magnet to align in one direction and

   their magnetic fields will reinforce and make it a permanent magnet

Magnetic field of a bar magnet

Method for determining the magnetic field of a bar magnet using a compass?

1. Place the bar magnet on a piece of paper and draw around it

2. Place the compass on the corner of one pole and mark the direction where the needle points

3. line the needle of the compass with this point and continue so until you reach the end of the bar magnet

4. Repeat for further lines and draw arrows from north to south

Two tests for magnetic field

plotting compass

iron filings

Law of magnetic fields

like poles will attract

unlike poles will repel

How does a compass work?

• the compass has a small magnet

• the north seeking pole of the compass will point to the Earth’s magnetic pole

How are magnets induced?

by placing in a magnetic field so domains align to the direction of attraction so have opposite polarity to magnet

Compare induced magnets and permanent magnets

Both:

• have a magnetic field

• attract magnetic material

• have poles

• contain domains

However:

• only permanent magnets retain magnetism

• induced magnets only attract

• induced magnets only have temporarily aligned domains