Question

Which of the following uses the principle of electromagnetic induction?
A) Doorbell
B) Water Cooler
C) Solar Cell
D) Electrical Battery

Answer 1

Hint: Electromagnetic Induction is a current produced because of voltage production of Electromotive Force due to a changing magnetic field. Electromagnetic Induction or Induction is a process in which a conductor is put in a particular position and the magnetic field keeps varying or the magnetic field is stationary and a conductor is moving.

Complete answer:
The magnetic field associated with a coil is the magnetic flux flowing normally to the surface area of the current-carrying coil.
When it changes, an electromagnetic force is produced opposing the cause. This is the principle of Electromagnetic induction.
Doorbell uses the principle of Electromagnetic Induction.

Hence Option (A) is correct.

Additional Information:
Did you know that the principle of electromagnetic induction is also involved in the working of a credit card strip when you swipe it across the card machine? How do you think this works? The strip is magnetic.

Note: Mathematically, the induced voltage can be given by the following relation:
$e= \dfrac{N d\phi}{dt}$
Where,
e is the induced voltage (in volts)
N is the number of turns in the coil
$\phi$ is the magnetic flux
t is the time (in seconds)
The significance of this discovery is a way of producing electrical energy in a circuit by using magnetic fields, and not just batteries. Everyday machines like motors, generators and transformers work on the principle of electromagnetic induction.