Simple phenomena of magnetism — IGCSE Physics Notes

There are two magnetic poles: north & south. Like poles repel, unlike poles attract. Magnets and magnetic material are influenced by magnetic fields.

Induced magnetism:

When magnetic material is placed in a magnetic field, the material can temporarily be turned into a magnet.
The magnet induces magnetism in them.
The induced pole of the magnetic material that is closer to the magnet is the opposite of the pole at the end of the magnet.

Magnets and induced poles: a nearby magnet temporarily magnetises soft iron, and the nearest induced pole is always opposite, so the iron is attracted

Temporary magnets	Permanent magnets
Only have magnetic field temporarily	Produce their magnetic field all the time
Made of soft iron	Made of steel

Magnetic Material	Nonmagnetic materials
Any object that can be influenced by magnetic fields, and has the potential to become a magnet.	Any object that cannot be influenced by magnetic fields.

Magnetic field – A region in which a magnetic pole experiences a force.

Direction of a magnetic field at a point – The direction of the force on the N pole of a magnet at that point.

Magnetic field around a bar magnet: field lines run from north to south outside the magnet, never cross, form closed loops, and are closer together where the field is stronger

Ways of plotting magnetic field lines:

With a compass. A compass can determine the direction of the magnetic field.
Iron filings.

Magnetic field between unlike poles: parallel, evenly spaced field lines give a nearly uniform field in the central gap, directed from the north pole to the south pole

Permanent magnets	Electromagnets
They stay magnetised.	A type of magnet in which the magnetic field is produced by an electric current.
They cannot be switched on and off.	They can be switched on and off.
Compasses, headphones, loudspeakers.	Electromagnetic cranes, electric bells.

Magnetic forces are due to interactions between magnetic fields.

The relative strength of a magnetic field is represented by the spacing of the magnetic field lines. The closer the lines, the stronger the magnetic field.