Explain the following terms.

(a) Directive property of a magnet

(b) Earth's magnetic field

(c) Single touch method

(d) Demagnetisation

(e) Magnetic keepers

(a) Directive property of a magnet: A freely suspended magnet always aligns itself in the north–south direction due to Earth’s magnetic field and this property of a magnet is known as the directive property of magnets which is used in a magnetic compass for navigation.

(b) Earth's magnetic field: The Earth itself behaves like a giant bar magnet, with a magnetic north pole near the geographic south pole and vice versa. The space around Earth where its magnetic force can be felt is called the Earth’s magnetic field and it helps in navigation using a compass.

(c) Single touch method: A method of making magnets where one pole of a permanent magnet is rubbed along the length of an iron bar from one end to the other which aligns the molecules of the iron bar such that it gets magnetised.

(d) Demagnetisation: The process of destroying magnetism of a magnet is called demagnetisation.
The demagnetisation of a magnet can be done in the following manner:

• By rough handling
• By dropping the magnet on the floor or on a hard surface a number of times
• By hammering the magnet repeatedly
• By heating the magnet to a very high temperature
• By passing alternating electric current around the magnet

(e) Magnetic keepers: Magnetic keepers are soft iron strips placed across the poles of a magnet when not in use which provide a closed path for magnetic lines of force, preventing self-demagnetisation and preserving the magnet’s strength.