Permanent & Induced Magnetism, Magnetic Forces & Fields Flashcards
All 24 cards in this deck
What is the rule for the force between magnetic poles?
Like poles repel, unlike poles attract.
What type of force is the attraction or repulsion between two magnetic poles?
A non-contact force — the magnets do not have to touch to exert a force on each other.
Name the four magnetic materials named in the specification.
Iron, steel, cobalt and nickel.
Which material is chosen for a part that must be easily magnetised and demagnetised, such as an electromagnet's core?
Iron — it is a magnetic material that is easily magnetised and demagnetised.
True or false? A bar magnet can repel an unmagnetised piece of iron.
False. The force between a magnet and a magnetic material is always attraction.
What is a permanent magnet?
A magnet that produces its own magnetic field all the time.
What is an induced magnet?
A material that becomes a magnet when it is placed in a magnetic field.
What happens to an induced magnet when it is removed from the magnetic field?
It loses most or all of its magnetism quickly.
What kind of force does induced magnetism always cause?
A force of attraction.
True or false? An induced magnet can repel the permanent magnet that induced it.
False. Induced magnetism always causes a force of attraction.
A steel paperclip is picked up by a bar magnet and hangs from it. Is the paperclip a permanent magnet or an induced magnet?
An induced magnet — it only becomes magnetic while it is in the magnet's field.
What is a magnetic field?
The region around a magnet where a force acts on another magnet or on a magnetic material.
Which way do magnetic field lines point?
From the north (seeking) pole of the magnet to the south (seeking) pole.
How is the direction of the magnetic field at a point defined?
It is the direction of the force that would act on another north pole placed at that point.
How does the strength of a magnetic field depend on position around a bar magnet?
It is strongest at the poles and gets weaker as distance from the magnet increases.
What does the spacing of the magnetic field lines in a field pattern tell you?
The closer together the lines, the stronger the field.
What does a magnetic compass contain?
A small bar magnet, free to turn.
When no other magnet is nearby, what direction does a compass needle point in?
In the direction of the Earth's magnetic field (its north-seeking pole points towards geographic north).
What is the behaviour of a compass evidence for?
That the Earth has its own magnetic field, so the Earth's core must be magnetic.
True or false? The magnetic field that makes a compass point north is produced in the Earth's atmosphere.
False. It is produced inside the Earth, which is evidence that the core is magnetic.
How does a compass needle behave when it is placed in the magnetic field of a bar magnet?
It lines up with the field, pointing along the field line from the magnet's north pole towards its south pole.
True or false? The needle of a magnetic compass is a permanent magnet.
True. It is a small bar magnet that keeps its own magnetic field.
What are the steps to plot the magnetic field pattern of a magnet using a plotting compass?
e.g. a bar magnet on a sheet of paper
- Draw round the magnet, place the compass near one pole and mark a dot at each end of the needle.
- Move the compass so its tail is on the last dot, and mark a new dot at its tip; repeat.
- Join the dots in a smooth line with an arrow from north to south.
When plotting a bar magnet's field with a compass, how do you get the whole field pattern rather than one line?
Repeat the chain of dots starting from several different points around the magnet.