Introduction
Activities using magnets can feature at all levels. Students will have some knowledge of magnets, since they are common around homes, but students often expect magnets to attract any metal object rather than only iron and steel. Magnets have no effect on aluminium, brass, silver or copper. Students will often not know what metal common objects are made of, and, in fact, some substances that look like metal are coated plastic, and some plastic-coated objects such as paperclips have metal within them.
Magnetic effects involve transformation of energy. Energy, however, is a difficult concept and it may well be worthwhile considering using magnetism to illustrate the concept of force. A force can be defined as ‘anything which can cause an object to start moving, stop moving or change its direction’.
A force cannot exist by itself: it can only be exerted by one object on another, for example:
- Earth attracting a stone (force of gravity)
- a magnet attracting a ferrous metal (magnetism)
- a child pushing a block or kicking a ball.
Key concepts of magnetism
The activities in this topic are designed to explore the following key concepts:
Early years
- Magnets push and pull some matter.
- Magnets do not push and pull all matter.
- Many toys contain magnets.
- Some magnets exert more force than others.
- Magnets have many different shapes.
- Magnets are used in many ways.
- Magnets are strongest at their ends.
- Ends of magnets may push or pull other ends of magnets.
Middle years
- Magnets act on objects made of iron or steel only.
- A magnet is surrounded by a magnetic field, of definite shape.
- Magnetic force extends into the space surrounding the magnet.
- Magnets push and pull through some types of matter but not others.
- Temporary magnets can be made from permanent magnets.
- Magnetism can be destroyed by rough handling or heating.
- Some rocks are natural magnets.
- A freely suspended magnet lines up in a north-south direction. A compass needle is a small magnet.
- Like poles of a magnet repel; unlike poles attract.
- Earth has a magnetic field.
- Electric currents have a magnetic field.
Students’ alternative conceptions of magnetism
Research into students’ ideas about this topic has identified the following non-scientific conceptions:
- Magnets are attracted to all objects made of metal.
- Big magnets are stronger than little ones.
- The magnetic and geographic poles of Earth are located at the same place.
- Magnetic poles are only at the ends of magnets.