Magnets

Magnets create forces without touching. They have two ends called poles: a north pole (N) and a south pole (S). You meet magnets in fridge doors, compasses, and headphones.

Magnetic poles and forces

• Like poles repel (N–N or S–S). Unlike poles attract (N–S).
• Magnets act on other magnets and on magnetic materials: iron, steel, nickel, cobalt.
• Non-magnetic materials (wood, plastic, copper, aluminium) are not attracted.

Induced magnetism

When a magnetic material is placed near a magnet, it becomes a magnet temporarily. This is called induced magnetism. It explains why a magnet attracts iron even if the iron was not a magnet before.

• Example: a chain of paperclips forms when the first one is magnetised by the magnet, and then magnetises the next.
• Induced magnetism causes attraction only between a magnet and unmagnetised iron.

Temporary vs permanent magnets

• Soft iron: magnetises easily, loses magnetism quickly (temporary). Used for electromagnets and keepers.
• Steel: harder to magnetise, keeps magnetism (permanent). Used for bar magnets and compass needles.

Magnetic fields and field lines

A magnetic field is the region where a magnetic pole experiences a force. Think of field lines as invisible arrows showing how a tiny north pole would move.

• Outside a bar magnet, field lines go from N to S.
• Closer lines mean a stronger field (strongest near the poles). Lines never cross.
• The direction of the field at a point is the direction of the force on a N pole.

Showing field patterns

• Iron filings: place paper over the magnet, sprinkle filings, and tap gently. Filings line up along field lines and bunch where the field is strong.
• Plotting compass: place a small compass near the magnet, draw an arrow showing the compass needle (north-seeking end). Move and repeat to map lines from N to S.

Uses of magnets

• Permanent magnets: fridge catches, compasses, magnetic door latches, small motors.
• Electromagnets: scrap-yard cranes (lifting iron/steel), relays and doorbells, speakers and headphones.

Making and caring for magnets

• Make a permanent magnet: stroke steel in one direction with a magnet, or use a strong direct current (DC) in a coil.
• Demagnetise: heating, hammering, or using an alternating current (AC) field. Store bar magnets with soft-iron keepers to reduce loss of magnetism.

Common misconceptions

• Magnets do not attract all metals—mainly iron, steel, nickel, and cobalt.
• A magnet and unmagnetised iron never repel; they always attract due to induced magnetism.
• A compass shows the field direction; its north-seeking end points along the magnetic field line.