The History of Magnetism
The video below shows a brief history of Magnetism
Permanent Magnetic Fields
Some materials are naturally magnetic. These include:-
Iron
Cobalt
Nickel
Rare Earth Metals such as Neodymium
All magnets generate a magnetic field around them.
A magnetic field is a region where a magnetic material will experience a Force.
We can see the shape of these fields by using Iron filings. The Iron filings are magnetic and "line up" with the magnetic field, showing its shape:-
Electromagnets
Permanent magnets are very useful in providing a long term fixed Force, but being able to turn a magnet on or off is much more useful.
When a Current flows in a wire, a magnetic field is formed around it. If that wire is coiled up the magnetic field can be made stronger. The magnetic field only exists when the Current flows, so the magnet can be easily turned on or off.
A simple electromagnet can be made by wrapping a wire around a piece of Iron such as a nail:-
The strength of an electromagnet depends on:-
The number of times it has been coiled (more coils, stronger magnet).
The Current flowing in the wire (higher current, stronger magnet).
The type of core used (Iron core, stronger magnet).
Magnetic Field Examples
The following diagrams show the shape of the magnetic field lines around several types of magnet:-
