Magnets and Magnetism Magnets have various shapes: Horseshoe magnet U-shaped magnet Rod magnet Button magnet Bar magnet Ring magnet

A magnet always settles in a north-south direction when suspended in the air. The end of the magnet pointing north is called the north-seeking pole or N-pole.

Unlike poles attract and Like poles repels. N NS N

NS N S Like Poles Repel Each Other. NS NS Unlike Poles Attract Each Other.

Every magnet produces its own magnetic field around itself. Lines of magnetic force are from the north pole to the south pole

Magnetic Materials Steel Nickel Iron Cobalt Non Magnetic Materials Zinc Pure Stainless Steel Copper Aluminium A magnet will only attract magnetic materials:

 Induction  Electric Methods  Stroking

When a magnetic material is attracted to a magnet it becomes a magnet and it is called induction. The magnet formed is called an induced magnet. S N Induced magnet

A piece of magnetic material can be permanently magnetised by stroking one pole of a bar magnet. The pole at the end of the stroke is always the opposite of the one used to stroke: South North

A piece of magnetic material such as steel bar is placed in coil of wire or solenoid which carries direct current for a short while. Steel nail

Magnetising by Electrical Method: Steel Makes better permanent magnet Does not lose magnetism easily Iron Makes better temporary magnet Loses magnetism easily

Methods of Demagnetising 1.Hitting or Hammering a magnet

Methods of Demagnetizing 2. Heating a magnet eg place it under the sun 3. Electrical Method: -By using an a.c. -A magnet will lose its magnetism if it is placed in a coil carrying an alternating current and then drawn to some distance away from the coil.

Electromagnets They are temporary magnets

Electromagnets Soft Iron makes good electromagnets because it loses magnetism easily. The iron is magnetized only when a d.c. is flowing.

Uses of Electromagnets To lift up iron and steel scrap metals in a scrap yard. In ear-pieces of telephones and loudspeakers In all motors

Differences between: Permanent Magnet Does not lose magnetism easily Made of Steel Does not depend on electric current for its magnetic force Temporary Magnet Loses magnetism when current is switched off Made of soft iron Is magnetized when a d.c. is flowing in the solenoid

Uses of Permanent Magnets Door and bag catches Magnetic strips in doors of refrigerators Magnetic strips in telephone cards, credit cards, stored value cards, ATM cards In a compass needle.

A Compass The compass needle is a permanent magnet, it will point towards the Earth’s magnetic North Pole.