Magnetic Fields – Observing Magnetic Force

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How can we observe the invisible magnetic field of a magnet?
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A magnetic field is the area around a magnet that has magnetic force. We can observe the magnetic field of a magnet using iron filings.

Place a bar magnet on the table and cover it with a sheet of paper. Gently sprinkle iron filings over the paper. Tap the paper to spread the filings out.

Wow! There it is! Notice that the magnetic field is strongest at each of the poles.

Let's see what happens when we add a second bar magnet and bring 2 like poles close together.

Look! there space between the poles doesn't have many iron filings. This is because the poles are repelling each other.

What do you think we'll observe when unlike poles are brought close together?

Cool! the iron filings are concentrated between the unlike poles because they attract each other.

Experiment by adding more magnets. Arrange them in different ways and observing the different patterns their field lines produce.

Check out our related videos to observe other ways magnets interact with other objects.

Non-contact Forces – Magnetic Force
Place an iron nail on a table. Slowly move a magnet towards the nail. What do you notice?

A magnet is an object with magnetic force. Magnetic force occurs in an object due to the motion of electrically-charged particles. As you observed when you moved the magnet near the iron nail, magnetic force can act at a distance. It is a non-contact force. It can act through solids, liquids and gases.

Magnetic force can attract objects made of certain metals such as iron and nickel. Magnetic force cannot attract objects made of plastic, wood, rubber or glass.

A magnet has two poles – a North pole and a South pole. It is at each pole that the magnetic force is the strongest.

When the like poles of two magnets are brought together, they push or repel each other. When unlike poles are brought together, they pull or attract each other.

Many objects make use of magnetic force. Some doors use magnets to keep them closed. Magnets are used to stick notes and photographs to refrigerators. They are used in electric motors, loudspeakers and can also be used for medical imaging and storing data on computer disks.

When a magnet is hanging freely, it will come to rest with the South pole pointing in the direction of north and the North pole pointing in the direction of south. A compass is a device that uses this property to find the direction of north.

A maglev (magnetic levitation) train has magnets that repel it from the track. This reduces friction and allows the train to travel at fast speeds.