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ICSE Class 7 Physics Question 18 of 36

Electricity and Magnetism — Question 18

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Question 18

Draw a neat and labelled diagram of an electric bell and describe its working.

Answer

Labelled diagram of the electric bell is shown below:

Draw a neat and labelled diagram of an electric bell and describe its working. Electricity and Magnetism, Concise Physics Solutions ICSE Class 7.

Working of electric bell:

  1. When the switch (bell push) is pressed, current flows through the coil of electromagnet.
  2. The electromagnet gets magnetized and attracts the armature. As the armature moves the hammer attached to it moves and strikes the gong so the bell rings.
  3. During this process the contact between the metallic springy strip and adjusting screw breaks so the circuit becomes incomplete.
  4. The current stops flowing through the coil of electromagnet and it gets demagnetized.
  5. As the electromagnet gets demagnetized, the armature comes back to its original position due to spring action of the metallic springy strip and comes in contact with the adjusting screw.
  6. The circuit becomes complete, if the bell push is pressed again, current will flows through the coils of electromagnet and it gets magnetized.
  7. It attracts the armature and hammer attached with it strikes the gong again and the bell rings.
  8. This process of making and breaking the circuit continues and the bell rings as long as the bell push remains pressed.