How Magnets Work

Magnets are usually made of metal iron, or another material that has lots of iron in it, such as steel. Magnets can be of various shapes, but all of them have the ability to pull things towards themselves. This invisible force is called magnetism. Magnets only attract (pull) metals that are made of iron or that contain iron.

Magnetism is concentrated around the poles (ends) of a magnet. A magnet has two poles, called the north pole and the south pole. The two poles may look the same but they behave differently. Put one pole of a magnet near to a pole of another magnet, and watch what happens. You may feel an attraction (pulling) force as the two poles stick together. Alternatively, you may feel a repulsion (pushing) force, as the two poles push away from each other. In all magnets, identical poles will repel (push away) each other. In all magnets, identical poles will repel (push away) each other, while different poles will pull towards each other.

TINY MAGNETS

Think of a bar of iron as having millions of micromagnets inside it. These are called domains. If they are all jumbled up, the bar is not a magnet. If the micromagnets in a bar are lined up and point the same way, it is a magnet.

ATTRACTION AND REPULSION

The poles of two magnets that are different or opposite will attract. Magnetic lines of force from north and south poles pull together and join. The poles of two magnets that are the same will repel or push each other apart.

SEEING MAGNETISM

You cannot see the magnetic force around a magnet, but you can see the effects of its presence when an iron nail sticks to a magnet. You can see he shape of a magnetic field by using tiny, powderlike pieces of iron, called iron fillings. Iron fillings reveal that the lines and strength of the magnetic force are concentrated around and between the poles at the end of the horseshoe magnet. On a bar magnet, they line up to show how the magnetic force spreads out from the poles (ends).

Is a big magnet more powerful than a small one? Not always. You cannot tell how powerful a magnet is just by looking at it. Compare the strength and power of different magnets in the project below.

STRENGTH OF A MAGNET

You will need :
Scissors, tape, round plastic container, two magnets, ruler, rubber bands, steel washers.

STEP 1
Cut off a piece of tape and use it to tape the round container firmly to the work surface. The round container will act as a pivot, or the balancer.

STEP 2
Attach a magnet to one end of the rubber band and some washers to the other end of the ruler. Position the middle of the ruler on the balancer.

STEP 3
Hold another magnet above the first. Lower it until the ruler tips over. Measure its height above the table. The higher it is when the ruler tips over, the stronger the magnet.

POWER OF A MAGNET

You will need :
Pencil, thumb tacks, strong thread, card, ruler with holes at both ends and in the middle, scissors, tape, rubber bands, adhesive dots, pen, two small bar magnets.

STEP 1
Attach one end of a piece of thread to a tack and the other to a pencil. Draw two large quarter-circles on card. The distance from the pin to curved edge should be as long as the ruler.

STEP 2
Draw a triangle in one quarter-circle and cut it out. Using the triangle as a template, cut out a triangle from the other quarter-circle. Tape them together.

STEP 3
Push a tack through the ruler's end hole, so that it pivots. Attach rubber bands from the ruler's middle hole to the quarter-circle's side. Add dots labeled N and S to each ruler end.

Stand the magnet measurer upright. Attach one magnet to the ruler's top end with a rubber band. Bring the unlike pole of another magnet near it. How far can it pull the ruler? Stronger magnets pull it farther.