Unit 4 Electricity and magnetism
Methods of magnetisation
- Stroking method
A bar of steel can be magnetised by stroking it with a bar magnet. The domains become aligned, and a N pole and a S pole are induced.
If a steel bar is placed so that it lies in the direction of the magnetic field lines of a strong magnet and then hammered gently, the domains will begin to line up in the direction of the field. As they do, the steel bar itself becomes magnetised. The effect can be increased by slightly heating the steel bar first.
- Electrical method
A bar of steel or iron can be magnetised by placing it in a coil of wire (solenoid). Passing a d.c. (direct current) through the wire will magnetise the bar.