Question

Which of these devices uses a magnet or electromagnet to make it work?
(A) An electric bell
(B) A compact disc
(C) A microchip
(D) All of the theses

Answer 1

Hint
Electromagnets are materials in which the magnetic field is produced by electric current. Electromagnets have a wide range of applications.

Complete step by step answer
The core of electromagnets are made of ferromagnetic material having low retentivity, high permeability and the suitable material for electromagnets is soft iron. A soft iron rod is placed in a solenoid and electric current is passed through it as shown in the figure, resulting in an increase in the magnetism of solenoid by thousand-fold. The magnetism is effectively switched off on switching off the current in solenoid because of the low retentivity of the soft iron core.

Electromagnets are used in electric bells, loudspeakers, telephone diaphragms, earphones, in cranes to lift machinery, etc. It has its applications in transformers as well. Electric bells consist of perfectly insulated wire coils that are wound over iron rods. The rods become magnetic when an electric current is passed through the coils, the rods attract iron attached to the clapper resulting in ringing. This means that when the amount of current is applied through an electric bell, it produces a repetitive bustling sound. Electric bells are used in fire alarms, rail crossings, telephones, school bells, doorbells, etc.
Therefore, (A) An electric bell, is the required answer.

Note Electric bells are now preferred to be replaced by electronic sounders. Electromagnets are used in the electric bells and not the permanent magnets.