4.1.2Electricity and Magnetism

Magnets — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions

5 min read 10 parts Lesson 6 of 65 1 quiz

📚 Cambridge IGCSE Physics 0625 Hub / Topical Revision

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Lesson summary

4.1.2 Magnets — IGCSE PHYSICS notes: Distinguish permanent and induced magnets and describe how to make, demagnetise and use magnets and electromagnets.Permanent magnet — made of a hard magnetic material such as steel, produces its own magnetic field and does not lose its magneti…

Induced (temporary) magnet
Attraction
Magnetised
Steel objects
Soft iron objects
Using a current

Part 1 of 8Permanent and induced magnets

Permanent and induced magnets

Permanent magnet

Permanent magnet made of a hard magnetic material such as steel, produces its own magnetic field and does not lose its magnetism

Induced (temporary) magnet

Induced (temporary) magnet a material with a soft iron core that becomes a magnet temporarily in a magnetic field

Attraction

Attraction induced magnetism always causes a force of attraction between the permanent magnet and the induced magnet

Magnetised

Magnetised the end of the material closest to the magnet has the opposite pole to the nearest magnet pole

Removal

Removal soft iron loses induced magnetism quickly and becomes unmagnetised

Part 2 of 8Steel and soft iron

Property	Soft iron	Steel
Magnetises	Easily	With difficulty
Keeps magnetism	No, it is temporary	Yes, it is permanent
Used for	Electromagnet cores, transformers, relays	Permanent magnets, compass needles

Steel objects

Steel objects paperclips and needles stay magnetic for a while

Soft iron objects

Soft iron objects electromagnets and transformers are unmagnetised as soon as the cause is removed

Part 3 of 8Making a magnet

Stroking

Stroking stroke steel many times with one pole of a magnet in the same direction, lifting the magnet well away between strokes
The end last touched becomes the opposite pole

Using a current

Using a current place steel inside a solenoid carrying direct current
The field lines up the domains
A higher current and more turns give a stronger magnet

Hammering

Hammering hammering steel lying north-south can magnetise it slightly using the Earth's field

Pole of a solenoid

Pole of a solenoid looking at one end, anticlockwise current makes a north pole and clockwise a south pole

Part 4 of 8Demagnetising a magnet

Heating

Heating strong heating destroys the magnetism

Hammering or dropping

Hammering or dropping scrambles the aligned domains

Alternating current

Alternating current place the magnet in a solenoid carrying alternating current and slowly withdraw it
The field keeps reversing
Its strength decreases as the magnet moves away

Storage

Storage keep magnets in pairs with opposite poles together and a soft iron keeper across the ends

Part 5 of 8Electromagnets

Construction

Construction a coil of wire wrapped on a soft iron core

Action

Action the core is strongly magnetised when current flows and loses its magnetism quickly when it stops

Strength

Strength raised by increasing the current, the number of turns or the size of the soft iron core

Advantage

Advantage magnetism can be switched on and off

Part 6 of 8Testing and choosing materials

1Test for magnet or material

Test for magnet or material bring the material close to a known magnet

2Choosing

Choosing steel for permanent magnets and soft iron where magnetism must be switched off

Part 7 of 8Applications of electromagnets

Applications of electromagnets

Cranes

Cranes lift scrap iron and steel

Electric bells and relays

Electric bells and relays use switched magnetism

Loudspeakers and earphones

Loudspeakers and earphones electromagnets produce the sound waves

MRI scanners

MRI scanners very powerful electromagnets produce images of organs

Mag-Lev trains

Mag-Lev trains electromagnets on the train and track repel and make the train hover

Part 8 of 8More from the specification

1Non-contact magnetic forces

Non-contact magnetic forces permanent magnets exert attractive or repulsive magnetic forces on nearby ferromagnetic specimens without physical contact.

2Magnetic Materials and Induced Magnetism

Magnetic materials include ferromagnetic metals such as iron, steel, nickel,
and cobalt,
whereas copper, aluminium,
and plastics are non-magnetic;
when a piece of unmagnetised ferromagnetic metal is brought near a permanent magnet, it is attracted towards either pole due to induced magnetism.

Mapping Magnetic Fields with Iron Filings and Plotting Compasses — Magnetic fields represent regions where magnetic materials experience a force; field lines can be visualised by sprinkling iron filings over paper,

or mapped point-by-point using small plotting compasses that point in the direction of the magnetic field from north to south.

4Magnetic Poles and Suspended Magnets

Like magnetic poles repel apart while opposite poles attract;
when a bar magnet is freely suspended horizontally, it rotates until its north pole points towards the Earth's geographic north, demonstrating the Earth's geomagnetic field.

5Plotting compass

Plotting compass small compasses placed around a magnet align with magnetic field lines to map their continuous shape.

6Iron filings

Iron filings sprinkling iron filings over card reveals magnetic field patterns as magnetic pieces align along field lines.

7Magnetic metals

Magnetic metals ferromagnetic metals such as iron, steel, nickel, and cobalt experience attraction towards external magnetic fields.

8Magnetic force

The force on a moving charge in a magnetic field

Key terms

Term	Meaning
Permanent magnet	Magnet that keeps its magnetism
Induced magnet	Magnet that is magnetic only while in a magnetic field
Soft iron	Material that magnetises and demagnetises easily
Electromagnet	Coil of wire on a soft iron core that is magnetic while current flows
Solenoid	Long coil of wire carrying a current

Avoid these mistakes

Using steel for an electromagnet core — soft iron is used because it demagnetises quickly.

Using alternating current to make a permanent magnet — direct current is used.

Saying an induced magnet repels the magnet that induced it — it is always attracted.

Stroking back and forth — stroke in one direction only and lift the magnet away between strokes.

Last updated: 18 October 2026