Magnetic force is a NON-CONTACT FORCE — acts at a distance without touching.
MAGNETIC MATERIALS:
Ferromagnetic materials are attracted to magnets.
Main ferromagnetic materials at GCSE: IRON, STEEL, NICKEL, COBALT.
Aluminium, copper, plastic, wood — NOT magnetic.
Only iron, steel, nickel and cobalt can become magnetised or be attracted to magnets.
Permanent and Induced Magnetism
PERMANENT MAGNETS:
Produce their own persistent magnetic field — they don't need an external field to be magnetic.
Retain magnetism when the external field is removed.
Made from HARD magnetic materials — steel, alnico alloys.
Hard materials are harder to magnetise but retain magnetism better.
Examples: bar magnets, horseshoe magnets, fridge magnets, compass needles.
INDUCED MAGNETS:
Temporarily magnetised by placing them in a magnetic field.
When the external field is removed, they LOSE their magnetism quickly.
Made from SOFT magnetic materials — IRON.
Soft materials are easier to magnetise and demagnetise.
Examples: iron nail picked up by a magnet; iron core in an electromagnet.
INDUCED MAGNETISM DIRECTION:
The induced pole nearest to the magnet's pole is ALWAYS OPPOSITE to that pole.
This is why magnets ATTRACT ferromagnetic materials — the near end becomes the opposite pole.
Magnetising and Demagnetising
MAGNETISING a material:
Rub with a permanent magnet always in the same direction (stroking method).
Place in a SOLENOID carrying DC — the field aligns the magnetic domains.
Hammer while held in the Earth's magnetic field (unreliable).
DEMAGNETISING:
HEAT — heating above the CURIE TEMPERATURE destroys magnetic domain alignment.
HAMMERING/VIBRATION — disrupts domain alignment.
ALTERNATING CURRENT (AC) in a solenoid — reverses field repeatedly, randomising domains.
MAGNETIC DOMAINS:
A magnet is made of tiny regions called DOMAINS — each domain acts like a mini-magnet.
In an UNMAGNETISED material: domains point in random directions → overall effect cancels.
In a MAGNETISED material: domains are aligned in the same direction → net magnetic field.
Magnetising aligns the domains; demagnetising randomises them.
⚠️ Common Mistake
Only IRON, STEEL, NICKEL and COBALT are magnetic materials. Aluminium and copper are NOT attracted to magnets. Permanent magnets (steel) retain magnetism. Induced magnets (iron) lose it when the field is removed.
📌 Key Note
Like poles repel; opposite poles attract. Permanent magnets: retain magnetism (steel — hard). Induced magnets: temporary, lose magnetism when external field removed (iron — soft). Magnetic materials: iron, steel, nickel, cobalt. Domains: aligned = magnetised, random = unmagnetised.
🎯 Matching Activity — Magnetic Properties
Match each statement to permanent magnet or induced magnet. — drag the symbols on the right to match the component names on the left.
Permanent magnet
Drop here
Induced magnet
Drop here
Both attract
Drop here
Demagnetising
Drop here
The near end always becomes the opposite pole — both are attracted to the magnet
Made from iron — temporary, loses magnetism when external field removed
Made from steel — retains magnetism without an external field
Heating above Curie temperature or using AC solenoid — randomises domain alignment
🎯 Test Yourself
Question 1 of 2
1. A steel paper clip is brought near a bar magnet. Why is the paper clip attracted?
2. A fridge magnet and a compass are both magnets. What is the key difference between them regarding their magnetism?
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