Example 1: testing for a magnet
Bar P attracts both ends of a compass needle. Is P a magnet?
- A magnet would repel one end of the needle.
- P attracts both ends, so it is a magnetic material, not a magnet.
This page needs the IB Demystified site-wide snippets. Ask the site administrator to install them.
IB DemystifiedMYP Sciences
Magnets and magnetic fields
Magnets hold notes on fridges, keep doors shut, sort scrap metal and guide travellers with compasses. They pull without touching, and the whole Earth behaves like a giant magnet.
Recommended for MYP 1 · About 3 lessons · Criteria A, B, C and D
On this page
Learning objectives
By the end of this topic you should be able to:
- describe magnetic poles and the forces between them
- identify magnetic and non-magnetic materials
- describe magnetic fields using field lines and compasses
- explain how a compass uses Earth's magnetic field
- describe simple electromagnets and uses of magnets
- plan fair tests and discuss magnet safety
Before you start
You will use these skills. If any feel shaky, review them first.
- forces and their effects (see Forces and their effects)
- simple circuits
- reading tables
Key vocabulary
- Magnetic pole
- The ends of a magnet, north and south, where the force is strongest.
- Magnetic material
- A material attracted by a magnet: iron, nickel, cobalt and steel.
- Magnetic field
- The region around a magnet where it exerts a force.
- Field line
- A line showing the direction of the field, from N to S outside a magnet.
- Compass
- A small magnet on a pivot that lines up with a magnetic field.
- Electromagnet
- A coil of wire that becomes magnetic when a current flows.
Understanding the ideas
-
What is it?
Every magnet has a north pole and a south pole. Like poles repel and unlike poles attract. Magnets attract magnetic materials such as iron, nickel, cobalt and steel, but not most other metals.
-
Why does it happen?
A magnet is surrounded by a magnetic field, shown by field lines that go from north to south; the field is strongest where the lines are closest, near the poles. Magnetism is a non-contact force that can act through many materials.
-
How do we know?
We can reveal a field with iron filings or plotting compasses. The Earth has its own magnetic field, which is why a compass needle points north.
-
Why does it matter?
Magnets and electromagnets are used in recycling, motors, speakers, door locks and hospital MRI scanners, but strong magnets must be handled safely.
-
What does it connect to?
Magnetism links to forces in physics, and later to electromagnetism, motors and generating electricity.
Magnet rules
- Like poles repel; unlike poles attract.
- Magnetic materials: iron, nickel, cobalt, steel. Copper, aluminium, plastic and wood are not magnetic.
- Only repulsion proves an object is a magnet.
- Field lines go from N to S; they are closest near the poles.
- Electromagnets get stronger with more turns, more current and an iron core, and can be switched off.
Magnets in the real world
Recycling centres use electromagnets to pull steel out of mixed waste. Hikers and sailors still carry compasses in case phones fail. Hospital MRI scanners use magnets strong enough to lift a car.
Worked examples
Example 2: reading a field
Where would a plotting compass point if placed just beyond the S end of a bar magnet?
- Field lines point into the south pole.
- The compass needle points towards the S pole.
Assessment tips
Questions on magnets often use field diagrams and simple tests. Expect to:
- Predict attraction and repulsion between poles.
- Identify magnetic materials.
- Draw and read field lines.
- Plan fair tests on magnet strength.
Common mistakes: saying all metals are magnetic; using attraction to prove something is a magnet; drawing field lines from S to N; and thinking a cut magnet gives separate poles.
Check your understanding
Quick questions on the ideas above. Try each one before using a hint.
Practice questions
Investigation: can a magnet pull through paper?
Partially guided investigation · about 35 minutes · pairs
- Research question
- How many sheets of paper can a fridge magnet hold a steel paperclip through before the clip falls?
- Scientific background
- Magnetic forces act through non-magnetic materials, but they get weaker with distance, so each extra sheet makes the pull weaker.
- Hypothesis
- Write your own prediction, with a scientific justification.
- Variables
- Identify your independent, dependent and control variables, and explain how you will control them.
- Apparatus
- Fridge magnet, steel paperclips, a stack of identical paper sheets, clamp or tape to hold the magnet, ruler.
- Method
- Fix the magnet under a table edge, facing down.
- Hold one sheet of paper against the magnet and see whether a paperclip stays attached underneath.
- Add sheets one at a time until the clip falls.
- Repeat three times and compare different magnets.
Safety. Keep strong magnets away from phones, bank cards and anyone with a pacemaker, and do not let them snap together on fingers.
Then evaluate: why did the clip eventually fall, even though paper is not magnetic?
Criterion-linked questions
Criterion B: inquiring and designing
Criterion C: processing and evaluating
Criterion D: reflecting on the impacts of science
Challenge questions
Harder problems in unfamiliar contexts. Plan before you calculate.
Topic check
Five questions picked at random from the whole topic. Take a new set whenever you like.
Review your mistakes
Questions you got wrong on this device appear here so you can try them again. Answer one correctly and it leaves the list.
Your progress
Tracked separately for each skill, on this device only.
| Skill | Correct | Status |
|---|