Question

Write a short note on electric bell. Explain it's construction and working with the help of the diagram. [5 Marks]

Answer 1

Construction of an electric bell.
Following are the components of electric bell:

• Electromagnet: A copper wire is wound around an iron piece which acts a magnet when current flows through it.
• Striker in touch with contact screw through an iron strip
• A metal gong
• A key or a switch [1.5 Marks]

[1.5 Marks]

Working of an electric bell

• When the switch is 'ON' and the screw is in contact with the iron strip, then electric current flows through the copper wire which gets magnetised because of electromagnetism.
• This magnetised copper wire (or the electromagnet) attracts the iron strip towards it, letting the striker hit the gong and thus sound is produced.
• As soon as the striker hits the gong, the screw loses its contact with the iron strip and therefore, current stops in the circuit.
• At this point, the electromagnet loses its magnetism and the iron strip moves back and comes in contact with the contact screw.
• The electric current is then restored in the circuit and again the striker hits the gong by the above process. This action repeats itself and the bell rings. [2 Marks]