Kinds of magnets and their uses
A fridge door stays shut because a magnet strip runs round its edge, and a toy train couples carriages with small magnets.
A magnet attracts some materials. Magnets come in many shapes: bar, horseshoe, ring or disc and button. The first magnet found in nature was magnetite (lodestone); today most magnets are made in factories. Magnets are used in fridge doors, speakers, pencil boxes, compasses and toys.
In the figure: Bar, horseshoe and ring magnets all have a north and a south pole.
Rule 1: Shapes — Each shape suits a job.
- Easy: Bar magnets are used in school experiments.
- Medium: A horseshoe magnet has both poles close together, so it lifts more.
- Exam-type: Ring and button magnets sit inside speakers and bags.
Rule 2: Uses — Look for a magnet in things that “snap” shut.
- Easy: Fridge doors, pencil boxes and cupboard latches use magnets.
- Medium: Magnetic strips on cards and toy trains also use them.
- Exam-type: Magnets can also separate iron from rubbish.
Look at an object’s shape and use, then guess where a magnet could be inside.
Thinking that every magnet is shaped like a bar.
"Bar, horseshoe, ring, button."
Practice questions
- 1Sailors in olden days used which device to find directions?
- 2Which everyday item often has a magnet to keep it closed?
- 3Which is a common shape of a magnet?
- 4In the story, who needed a way to find directions without seeing the stars?
- 5Naturally occurring magnets discovered in ancient times are called —
- 6The magnets in school laboratories, pencil boxes and toys are —
- 7Magnets can be made from pieces of —
- 8Why is a compass useful when clouds hide the stars?
Show answers (try them yourself first)
- 1A magnetic compass
- 2A pencil box
- 3Bar
- 4Sailors
- 5lodestones
- 6artificial magnets
- 7iron
- 8Its magnet settles in a north-south direction without needing the sky
Magnetic and non-magnetic materials
A magnet picks up iron pins from a heap but ignores plastic buttons and wooden pencils in the same heap.
Materials that a magnet attracts are magnetic; the main ones are iron, nickel and cobalt, and steel made from iron. Materials such as wood, plastic, glass, rubber, paper, copper and aluminium are non-magnetic. A material is tested by bringing a magnet near it.
In the figure: Iron objects are attracted; wood and plastic are not.
Rule 1: Sorting by testing — Bring the magnet near each object in turn.
- Easy: An iron nail, a steel pin and a nickel coin are attracted.
- Medium: A wooden ruler, plastic comb and glass marble are not.
- Exam-type: Copper and aluminium are metals but non-magnetic.
Rule 2: Not every metal is magnetic — Do not guess by looks; test.
- Easy: A shiny gold ring is not attracted.
- Medium: A steel spoon may be attracted, depending on the steel.
- Exam-type: The result of the test, not the look, decides.
Record each test in a table: object, material, attracted or not.
Saying that all metals are magnetic.
"Iron, nickel, cobalt: the magnet’s friends."
Practice questions
- 1Which paper clip is likely to be attracted by a magnet?
- 2Along with iron, which two metals are also magnetic?
- 3Which object is non-magnetic?
- 4Which set contains only magnetic metals?
- 5Materials that are attracted towards a magnet are called —
- 6The metal iron is —
- 7Materials that are not attracted by a magnet are called —
- 8Iron filings are —
Show answers (try them yourself first)
- 1One made of iron
- 2Nickel and cobalt
- 3A wooden ruler
- 4Iron, nickel, cobalt
- 5magnetic materials
- 6a magnetic material
- 7non-magnetic materials
- 8very small pieces of iron
Poles of a magnet and the Earth
Iron filings sprinkled on a magnet crowd together at its two ends; the middle stays almost bare.
The ends where a magnet pulls most strongly are its poles: the north pole and the south pole. They can never be separated; a broken magnet gives two smaller magnets, each with two poles. A freely hanging bar magnet settles in the north–south direction because the Earth behaves like a huge magnet.
In the figure: Filings gather at the poles at the two ends of the bar.
Poles of a magnet and the Earth
In the app you can move this figure with your finger.
Open in the appRule 1: Two poles always — You cannot make a one-pole magnet.
- Easy: Every magnet has a north pole and a south pole.
- Medium: Cut a bar magnet in two and each piece has both poles.
- Exam-type: Poles are strongest at the ends and weak in the middle.
Rule 2: The Earth as a magnet — A free magnet always lines up the same way.
- Easy: A hanging bar magnet comes to rest pointing north–south.
- Medium: The end that points north is the north-seeking pole.
- Exam-type: That is why old sailors trusted a floating magnet to find direction.
Always label both poles on the diagram, N and S.
Saying that a magnet can have just one pole.
"Break a magnet, get two magnets."
Practice questions
- 1Where do the maximum iron filings stick on a bar magnet?
- 2Which part of a bar magnet attracts the fewest iron filings?
- 3The ends of a magnet are called its —
- 4Most iron filings stick near the —
- 5Can a magnet have only a single pole?
- 6A student cuts a magnet into two hoping to get separate North and South pieces. What happens?
- 7The two poles of a magnet are named —
- 8If a bar magnet is broken into pieces, each piece has —
Show answers (try them yourself first)
- 1Near its ends
- 2The middle
- 3poles
- 4ends (poles) of the magnet
- 5No, poles always exist in pairs
- 6Each half has its own North and South pole
- 7North pole and South pole
- 8both North and South poles
Magnetic compass and making a magnet
A traveller in a forest looks at a small compass to learn which way is north.
A magnetic compass has a light magnetic needle that turns freely on a pivot inside a box marked with directions. The needle’s north-seeking end settles towards north, so we can find all other directions. A piece of iron or steel can be made into a magnet by stroking it many times in one direction with one pole of a strong magnet.
In the figure: The coloured end of the compass needle points to north.
Rule 1: Using the compass — Keep the compass flat, away from iron and magnets.
- Easy: Wait until the needle stops moving.
- Medium: Turn the box until N on the dial meets the needle’s north end.
- Exam-type: Now east, south and west can be read from the dial.
Rule 2: Making and keeping a magnet — Strokes in the same direction line up the iron’s tiny parts.
- Easy: Stroke an iron nail from one end to the other with the same pole, lifting the magnet away each time.
- Medium: After about 30 strokes the nail picks up pins.
- Exam-type: Heating, hammering or dropping a magnet weakens it; keep magnets in pairs with iron keepers.
Keep the compass flat and away from any iron before reading the direction.
Rubbing the iron back and forth instead of one way.
"One way, same pole, lift, repeat."
Practice questions
- 1About how many times is the stroking repeated to make the needle a magnet?
- 2The needle of a magnetic compass is a —
- 3A compass needle comes to rest along the —
- 4A magnetic compass is used to find —
- 5How can you check that a needle has become a magnet?
- 6In the floating-needle compass, after each rotation the needle ends point —
- 7The end of the compass needle that points north is usually painted —
- 8The compass needle is mounted on a pin so that it can —
Show answers (try them yourself first)
- 130 to 40
- 2small magnet
- 3north-south direction
- 4directions
- 5It attracts iron filings or steel pins
- 6in the same north-south direction
- 7red
- 8rotate freely
Attraction, repulsion and magnetic effect
Two fridge magnets pull together one way round and push apart when you turn one of them.
Unlike poles (north and south) attract each other; like poles (north–north or south–south) repel. A magnet’s pull works at a distance and even through paper, cloth or a thin sheet of wood. Repulsion is the sure test for a magnet, because a plain piece of iron is only ever attracted.
In the figure: N and S attract; N and N repel.
Rule 1: Attract or repel — Compare the two poles facing each other.
- Easy: North facing south: they attract.
- Medium: North facing north, or south facing south: they repel.
- Exam-type: Turning one magnet round changes attraction into repulsion.
Rule 2: Force through other things — The magnetic force weakens with distance.
- Easy: A magnet below a sheet of paper moves a pin lying on the paper.
- Medium: The pin is moved even though the magnet does not touch it.
- Exam-type: Repulsion shows the object is a magnet; attraction alone does not.
To test for a magnet, try both ends of each object against a known pole.
Saying that attraction proves an object is a magnet.
"Opposites attract, likes repel."
Practice questions
- 1Unlike poles of two magnets —
- 2Like poles of two magnets —
- 3An iron bar is attracted by —
- 4The South pole of a magnet brought near the North pole of a compass needle makes the needle —
- 5Two matchbox cars with magnets, like poles facing each other, will —
- 6The North pole of one magnet is brought near the South pole of another. They —
- 7Two North poles are brought near each other. They —
- 8How can you distinguish a magnet from an iron bar?
Show answers (try them yourself first)
- 1attract each other
- 2repel each other
- 3both poles of a magnet
- 4move towards the magnet
- 5run away from each other
- 6attract
- 7repel
- 8A magnet can repel another magnet; an iron bar is always attracted