Question

Which of the following devices works on the principle of electromagnetic induction?
A) Ammeter
B) Voltmeter
C) Generator
D) Galvanometer

Answer 1

Hint: When magnetic flux linking a conductor is changed, an emf or electromagnetic force is induced. This phenomenon is known as electromagnetic induction.
This principle of electromagnetic induction is used to power many devices. So, due to this principle, we can get voltage or emf as an output.

Complete solution:
Electromagnetic induction was first discovered by Faraday’s, therefore, it is also known as Faraday’s laws of electromagnetic induction.
Thus we can say, the basic requirement for electromagnetic induction to take place is that:
(i) There should be a change in magnetic flux linking the coil.
(ii) The induced electromagnetic force or current should persist as long as the change in magnetic flux takes place.
Faraday’s gave two laws for electromagnetic induction:
First law: When magnetic flux linking a conductor changes, an emf is induced in it. The induced emf lasts as long as the change in magnetic flux continues.
Second law: The magnitude of the induced emf in the conductor is directly proportional to the rate of change of flux linkages.
We know, the generator basic principle of operation, is electromagnetic induction.
When a change in flux linkages is changed, an emf or voltage is induced, thus we get voltage and hence current as our output which is desired for generators.
We know, in generators, the input is mechanical and the output is electrical. So, with this change in the magnetic field, we get an induced emf and hence current.
The mechanical force is used to bring in the changes in magnetic flux which in turn produces electricity.

Therefore, option (C) is correct.

Note: From the above discussion, it is evident that the induced current or the induced emf is proportional to the change in the magnetic field, thus with increasing the changes in magnetic flux linkages, more electricity can be generated.