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4.1.1Electricity and Magnetism

Magnetism — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions

5 min read 11 parts Lesson 5 of 65 2 quizzes

📚 Cambridge IGCSE Physics 0625 Hub / Topical Revision
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Lesson summary

4.1.1 Magnetism — IGCSE PHYSICS notes: Describe magnetic poles, forces between magnets and uses of permanent magnets and electromagnets.Poles — the ends of a magnet, one north and one southStrength — magnetic forces are strongest at the polesCompass — a freely suspended bar magne…

  • Like poles
  • Force type
  • Equal and opposite
  • Predicting
  • Magnetic metals
  • Non-magnetic

Part 1 of 9Poles of a magnet

Poles
  • Poles the ends of a magnet, one north and one south
Strength
  • Strength magnetic forces are strongest at the poles
Compass
  • Compass a freely suspended bar magnet lines up roughly north-south, which is how a compass works

Part 2 of 9Forces between magnets

Forces between magnets
Like poles
  • Like poles a north pole repels a north pole and a south pole repels a south pole
Unlike poles
  • Unlike poles a north pole attracts a south pole
Force type
  • Force type a non-contact force that weakens as the separation grows
Equal and opposite
  • Equal and opposite each magnet feels a force of the same size in the opposite direction
Predicting
  • Predicting work out the interaction from the arrangement of the poles

Part 3 of 9Magnetic materials

Magnetic metals
  • Magnetic metals iron, cobalt and nickel, and steel because it is an alloy containing iron
Non-magnetic
  • Non-magnetic copper, aluminium, wood, plastic and glass
Attraction
  • Attraction magnetic materials are attracted to both poles of a magnet

Part 4 of 9Testing an object

1Repelled by a known magnet
  • Repelled by a known magnet the object is a magnet
2Attracted
  • Attracted the object is a magnetic material
3Neither
  • Neither the object is non-magnetic
4Repulsion test
  • Repulsion test only repulsion proves an object is a magnet, because magnets also attract unmagnetised iron

Part 5 of 9Induced magnetism

1Process
  • Process an unmagnetised piece of iron or steel near a magnet becomes magnetised and is attracted
2Poles
  • Poles the end nearest the magnet becomes the opposite pole, so a north pole induces a south pole at the near end of a nail
3Paper clips
  • Paper clips each clip becomes a temporary magnet and induces magnetism in the next
4After removal
  • After removal soft iron loses almost all its magnetism and steel keeps some

Part 6 of 9Domain model

Domains
  • Domains atoms act as tiny magnets grouped in regions called domains
Unmagnetised
  • Unmagnetised domains point in random directions and cancel
Magnetised
  • Magnetised many domains line up in the same direction, giving a north and a south pole
Loss of magnetism
  • Loss of magnetism heating, hammering or dropping a magnet shakes the domains out of line
Cutting
  • Cutting a magnet cut in half gives two smaller magnets, each with both poles

Part 7 of 9Uses of permanent magnets

Compasses
  • Compasses for navigation, since the needle always points north
School experiments
  • School experiments the magnets used are permanent magnets
Toys
  • Toys toy trains and trucks use magnets to attach carriages
Fridge magnets
  • Fridge magnets flexible magnetic material or magnets stuck to a backing
Data storage
  • Data storage credit cards and hard disks store information in patterns of magnetised material

Part 8 of 9Uses of electromagnets

MRI scanners
  • MRI scanners powerful electromagnets in large cylindrical machines produce diagnostic images of organs
Speakers and earphones
  • Speakers and earphones electromagnets sense or send sound waves
Recycling
  • Recycling steel is separated from other materials by electromagnets and then reused, reducing mining for iron ore
Mag-Lev trains
  • Mag-Lev trains repelled by large electromagnets on the train and track, so they hover
  • Less friction
  • Speeds of nearly 640 km/h

Part 9 of 9More from the specification

More from the specification
Mapping Magnetic Fields with Iron Filings
  • Sprinkling iron filings onto paper over a bar magnet visualises magnetic field patterns,
  • as the filings align along continuous magnetic field lines.
Plotting Compasses and Field Direction
  • A small plotting compass placed in a magnetic field aligns with field lines, pointing its north-seeking pole towards the magnetic south pole of the magnet.
Density and Spacing of Field Lines
  • Magnetic field lines that are close together represent a strong magnetic field,
    • (near magnetic poles)
  • whereas lines that are far apart indicate a weaker field.
Magnetic Force Interactions
  • Like magnetic poles repel each other while unlike poles attract, mediated by the overlapping interaction of their surrounding vector magnetic fields.
Field
  • Region in which an object experiences a force at a distance
Magnetic field
  • Area around a magnet where its effects can be detected.
Field lines
  • Lines showing the direction and strength of a magnetic field.

Key terms

TermMeaning
PoleEnd of a magnet where the force is strongest
Magnetic materialMaterial attracted by a magnet, such as iron, cobalt, nickel and steel
Induced magnetismMagnetism produced in a magnetic material by a nearby magnet
DomainRegion in which atomic magnets point the same way
Non-contact forceForce that acts without the objects touching

Avoid these mistakes

1
Saying all metals are magnetic — only iron, cobalt, nickel and steel are.
2
Saying attraction alone shows an object is a magnet — only repulsion does.
3
Saying like poles attract — like poles repel.
4
Saying a magnet cut in half has one pole each — each piece has a north and south pole.

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