4.1Unit 9: Magnetism and electromagnets
Magnetic fields — Cambridge Checkpoint Physics 0893 Revision Notes & Topical Questions
5 min read 9 parts Lesson 1 of 4 1 quiz
Lesson summary
4.1 Magnetic fields — CHECKPOINT PHYSICS 0893 notes: Describe magnetic fields, draw field lines and explain how magnets interact.Magnet = an object that attracts magnetic materialsMagnetic materials — the metals iron, steel, nickel and cobaltSteel — a mixture that contains a larg…
- Surrounds all magnets
- Attraction
- Join poles
- Do not touch
- Do not cross
- Stronger magnet
Section 1 of 9Magnets and magnetic materials
Magnet
Magnet an object that attracts magnetic materials
Magnetic materials
- Magnetic materials the metals iron, steel, nickel and cobalt
Steel
- Steel a mixture that contains a large proportion of iron, so a paperclip is attracted
Poles
- Poles every magnet has a north pole and a south pole, shown as N and S
Section 2 of 9Magnetic field
Magnetic field
Magnetic field the area around a magnet where the effects of the magnet can be detected
Surrounds all magnets
- Surrounds all magnets and is strongest at the poles
Distance
- Distance a paperclip is attracted only inside the magnetic field of the magnet
Section 3 of 9Detecting a magnetic field
Attraction
- Attraction see whether a magnetic object moves towards the magnet
Compass
Compass a magnetised needle free to turn, which points along the direction of the magnetic field
Pattern
- Pattern iron filings sprinkled on paper over a magnet show the field pattern
Section 4 of 9Magnetic field lines
Join poles
- Join poles field lines join opposite poles
Direction
- Direction arrows point from north to south
Do not touch
- Do not touch the lines must not touch each other
Do not cross
- Do not cross the lines must not cross each other
Strength
- Strength the field is strongest where the lines are closest together
Stronger magnet
- Stronger magnet its lines are closer together and extend further away
Section 5 of 9Forces between magnets
| Poles facing | Force | Field lines between them |
|---|---|---|
| North and south | Attract | All point in the same direction |
| North and north | Repel | Point in opposite directions |
| South and south | Repel | Point in opposite directions |
Section 6 of 9Showing a field pattern with iron filings
1
Cut a hole in thick card just large enough to hold a bar magnet and place the magnet in it.
2
Lay a sheet of paper over the card so the magnet is under the middle.
3
Sprinkle iron filings gently and evenly over the paper.
4
Tap the paper gently so the filings move into position.
5
Observe the pattern and note where the filings are closest together.
6
Return the filings to the container by bending the paper into a channel.
Section 7 of 9Detecting a magnetic field with a paperclip
1
Place a magnet, a ruler and a paperclip on a smooth surface.
2
Slowly move the paperclip towards one pole of the magnet.
3
Record the distance d from the pole when the paperclip becomes attracted.
4
Repeat twice more and calculate the average.
5
Turn the magnet round and repeat for the other pole.
6
Interpret a larger d as a stronger magnetic field.
Section 8 of 9Key terms
| Term | Meaning |
|---|---|
| Magnet | Object that attracts magnetic materials. |
| Magnetic field | Area around a magnet where its effects can be detected. |
| Field lines | Lines showing the direction and strength of a magnetic field. |
| Pole | End of a magnet where the field is strongest. |
| Compass | Instrument with a magnetised needle that points along a field. |
| Like poles | Poles of the same type, which repel. |
Section 9 of 9Exam technique
1
Thinking field lines can cross — they never cross or touch.
2
Thinking all metals are magnetic — only iron, steel, nickel and cobalt are.
3
Thinking the field is strongest in the middle of the magnet — it is strongest at the poles.
4
Thinking a compass needle points to the north of any magnet — it points along the field lines.
Marked practiceQuizzes for this lesson
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