(i) Write two characteristics of a material used for making permanent magnets.
(i) Why is core of an electromagnet made of ferromagnetic materials ?

Explanation

(i) A material used for making permanent magnets should have high retentivity so that the magnet is strong and high coercivity so that the magnetisation is not erased by stray magnetic fields.
(ii) The core of an electromagnet is made of a ferromagnetic material like soft iron which has high permeability. On placing a soft iron rod in a solenoid and passing a current the magnetism of the solenoid is increased thousand fold and a strong electromagnet is prepared.