PROPERTIES OF MAGNETS 1. ALL magnets have NORTH and south poles. 2. When freely suspended, all magnets point to the north- Directional property. NORTH seeking pole SOUTH seeking pole

Magnetic materials. Materials that can be attracted by a magnet. These include: Iron(steel), Nickel, Cobalt or their alloys ONLY. Non-magnetic materials. Materials that do not feel a magnetic force.  Example: wood, copper, aluminium, rubber, water, wool, paper,

FEROUS MATERIALS Ferrous materials are materials that contain iron in them. Example: Steel, stainless steel, invar. Most ferrous materials are magnetic. NON-FERROUS MATERIALS These are materials that do not contain iron in them. Example: Nickel and cobalt which are magnetic. Most non-ferrous materials are non-magnetic.

THE LAW OF MAGNETISM Like poles repel, unlike poles attract.

Breaking a magnet produces two magnets. NS N S N N S S Repeated breaking will create a smallest magnet atomic magnet(dipole)

Un-magnetized material Domains are not arranged in any order. Magnetized material Domain aligned in one direction.

MAGNETIZATION A process of making of magnets. There are 3 methods of magnetising; 1. Stroking or touching. 2. Electrical method. 3. Magnetic induction.

Methods of magnetization

Magnetic induction When a magnetic material is close to a magnet, it becomes a magnet itself We say it has induced magnetism N S N S magnet

Soft Magnetism Pure iron is a soft magnetic material It is easy to magnetise iron but loses its magnetism easily. It is used to make (temporal) electromagnets N S beforeafter Iron nail S N N S Not a magnet N

Hard Magnetism Steel is a hard magnetic material It is harder to magnetise, but keeps its magnetism (it is used to make permanent magnets!) N S beforeafter Steel paper clip N N S It’s a magnet! N S SN

Magnetic fields The space around a magnet where it’s magnetic force is felt. The magnetic field is shown by field lines running from North pole to south pole

Magnetic field Patterns

A magnet has strong field at the poles.

ELECTROMAGNETS An ELECTROMAGNET is a magnet that can be switched on and off by an electric current. Switch On: Current flows and the nails becomes a magnet. Switch Off: No current and the nail looses its magnetism.

Increasing the strength of electromagnets 1. Increase amount of current. –More current produces stronger electromagnet 2. Increase number turns of the coil. 3. Using soft Iron core.

Uses of electromagnets 1.Used in lifting scrap metal 2.Used in many electronic devices such es electric bell, electric relay, loud speakers, etc.