Magnetism Flashcards
All 18 cards in this deck
What is the rule for the force between magnetic poles?
Like poles repel; unlike poles attract.
Name four magnetic materials.
Iron, steel, cobalt and nickel.
What is an induced magnet?
A magnetic material that becomes a magnet only while it is placed in (or near) a magnetic field, and loses its magnetism when the field is removed.
True or false? An induced magnet can repel a permanent magnet.
False. The force between an induced magnet and the magnet inducing it is always attraction.
Which of iron and steel is used for permanent magnets and which for temporary magnets, and why?
Steel for permanent magnets (it keeps its magnetism); iron for temporary magnets (it is easily magnetised but loses its magnetism quickly).
What are the steps of an experiment to show that iron becomes a temporary induced magnet?
e.g. using a bar magnet, an iron bar and paper clips
- Place the iron bar in contact with (or near) the magnet.
- Paper clips are attracted to the iron, and the first clip can pick up another.
- Remove the magnet — the clips are no longer attracted and fall off, so the magnetism was temporary.
In which direction do the magnetic field lines around a bar magnet point?
Out of the north pole, round and into the south pole.
Where is the magnetic field of a bar magnet strongest, and how do the field lines show this?
Just outside the poles (N and S), where the field lines are closest together — closer lines mean a stronger field.
Describe the field lines of a uniform magnetic field.
Straight, parallel and equidistant lines, all in the same direction — the field has the same strength everywhere.
Which part of the Earth generates its magnetic field, and what produces it?
The (magnetic outer) core — moving charges/ions in it.
Which way does a compass needle point when it is placed at a point in a magnetic field?
Along the field line at that point, with its north end pointing in the direction of the field.
True or false? The magnetic pole of the Earth near its geographic North Pole is a magnetic north pole.
False. It is a magnetic south pole — that is why the north end of a compass needle is attracted towards it.
What is the behaviour of a magnetic compass evidence for about the Earth?
The needle points along a magnetic field, so the Earth has a magnetic field — it behaves as if there were a magnet inside it, showing the core is magnetic.
What are the steps to use one plotting compass to find the shape and direction of a magnetic field?
e.g. around a bar magnet on paper- Place the compass near the magnet and mark the direction of the needle.
- Move the compass on to continue the field from that mark.
- Join the marks to reveal the overall field shape.
When plotting compasses are placed around a model of the Earth, how should the sketched field lines relate to them?
The field lines outside the Earth should line up with the compass needles, and continue inside the Earth towards the imaginary poles.
What is a permanent magnet?
A magnet that always has its own magnetic field, whether or not it is near another magnet or magnetic field.
Give one use of a temporary (induced) magnet.
The soft iron core of an electromagnet, e.g. in an electric door lock: the iron is magnetised only while current flows, so the lock can be switched on and off.
What is a magnetic field?
The space around a magnet in which a magnetic material, or another magnet, is pushed or pulled by a magnetic force.