Magnetism Flashcards

All 19 cards in this deck

What is the rule for forces between magnetic poles?

Unlike poles attract, like poles repel.

Name the magnetic materials you need to know.

Iron, steel, nickel and cobalt.
Copper, aluminium, plastic and wood are not magnetic.

The north end of a plotting compass needle points towards one end of a bar magnet. Which pole of the magnet is that end?

The south pole — unlike poles attract.

What is an induced magnet?

A material that becomes a magnet when placed in a magnetic field, and loses its magnetism when the magnet is removed.

True or false? A paper clip picked up by a magnet has become a permanent magnet.

False. It is an induced (temporary) magnet — the magnetism is lost when the magnet is removed.

Which is more suitable for making a temporary magnet (such as an electromagnet core), iron or steel?

Iron (soft iron) — it loses its magnetism easily when the field is removed, whereas steel keeps its magnetism, so steel is better for permanent magnets.

In which direction do magnetic field lines point outside a magnet?

From the north pole to the south pole.

Where is the magnetic field around a bar magnet strongest?

At (close to) the poles, where the field lines are closest together.

Describe the magnetic field lines of the uniform field between the north pole of one magnet and the south pole of another facing it.

Straight, parallel, equally spaced lines going from the north pole to the south pole.

What are the steps to use plotting compasses to show the shape and direction of the field around a bar magnet?
e.g. a bar magnet on a sheet of paper

1. Place a compass near the magnet and mark the direction the needle points with dots.
2. Move the compass to various positions and plot more points.
3. Join the dots to give several field lines, with arrows from north to south.

What are the steps to show that the Earth has a magnetic field?
e.g. using a plotting compass on a bench with no magnets nearby

1. Use a compass, away from any magnets.
2. It always points in the same direction — north.
3. So the Earth must have a magnetic field.

What does the behaviour of a magnetic compass tell us about the core of the Earth?

The core must be magnetic — the Earth has a magnetic field with a north and a south pole.

Apart from a compass, what could be used to show that the Earth has a magnetic field?

A suspended (bar) magnet, or a magnetised needle on a cork floating in water.

True or false? A phone app measuring magnetic field strength on a table with no magnets nearby should read zero.

False. It still measures the Earth's magnetic field.

True or false? Showing that a paper clip is attracted to a magnet proves the paper clip has kept some magnetism.

False. Any magnetic material is attracted to a magnet; only repulsion shows the paper clip is itself magnetised.

What is a uniform magnetic field?

A magnetic field that has the same strength and the same direction at every point.

What is a permanent magnet?

A magnet that makes its own magnetic field at all times, e.g. a bar magnet. It does not need to be in another magnetic field.

Why can a large magnet pick steel cans out of mixed waste but not aluminium cans?

Steel is a magnetic material, so the steel cans become induced magnets and are attracted to the magnet. Aluminium is not magnetic, so those cans are left behind.

What is a magnetic field?

The region around a magnet in which it exerts a force on magnetic materials or on other magnets.