Describe the forces between magnets, and between magnets and magnetic materials
Opposite (unlike) poles attract, and like poles repel. If permanent magnets are repeatedly knocked, the strength of their magnetic field is reduced. Converting a magnet to a non-magnet is called demagnetisation. Magnets are made from magnetic metals - iron, nickel and cobalt.
Give an account of induced magnetism
When a piece of unmagnetised magnetic material touches or is brought near to the pole of a permanent magnet, it becomes a magnet itself. The magnetism is induced. A North Pole induces a North Pole in the far end.
Draw and describe the pattern and direction of magnetic field lines around a bar magnet
It would be difficult to draw the results from the sort of experiment seen in the photograph so we draw simple magnetic field lines instead. A bar magnet with several curved lines pointing from the north to South Pole In the diagram, note that: - the field lines have arrows on them - the field lines come out of N and go into S - the field lines are more concentrated at the poles The magnetic field is strongest at the poles, where the field lines are most concentrated. Two bar magnets: Magnetic field lines for fields involving two magnets. Note the different patterns seen when two like poles are used and two opposing poles are used.
Oops! This image does not follow our content guidelines. To continue publishing, please remove it or upload a different image.
Distinguish between the magnetic properties of soft iron and steel
Iron gets magnetised faster but loses its magnetism as soon as the inducing magnet is removed. Hence soft iron is said to have high susceptibility but low retentivity. Core in the transformer is made up of soft iron material. Steel is slow to be magnetised but retains the acquired magnetism for a long time.
Distinguish between the design and use of permanent magnets and electromagnets
Electromagnets are objects that become magnetic when electricity is flown through it. They are temporary, as their magnetism can be turned on and off by switching an electrical circuit on and off.
Permanent magnets magnetism cannot be turned on and off, they are permanently magnetised.
Describe methods of magnetisation to include stroking with a magnet, use of direct current (d.c.) in a coil and hammering in a magnetic field
Stroking Method:
Procedure:
The steel bar is stroked with the same pole of the permanent magnet from one end to the other end in one direction.
