Question

Induced emf has:
(A) A direction same as field direction
(B) A direction opposite as field direction
(C) No direction of its own
(D) None of these

Answer 1

Hint: We know that when the flux linkages through the coil is changed, then a voltage is produced. This voltage is known as the induced emf. Faraday’s law of electromagnetism gives two laws and using them we can obtain the direction of the induced emf as well as its magnitude.

Complete Step-By-Step solution:
We know that flux linkages are calculated by multiplying flux with the number of turns of the coil. When there is change in flux linkages of this coil, then emf is induced.
Thus, when a magnet is moved towards the coil or away from it, the flux linking the coil changes and thus emf is induced.
Using Faraday’s laws of electromagnetic induction, we can obtain the magnitude and direction of induced emf. According to Faraday’s first law of electromagnetic induction, when the flux linking the coil is changed, emf is induced in the coil, and this continues as long as the change in flux linking the coil continues.
The other law of Faraday states that the magnitude of the emf induced is directly proportional to the rate of change of flux linkages.
Lenz’s law gives the direction of the induced emf and hence current. The law states that induced current flows in such a direction such that it opposes the cause that produces it.
Thus we can say, it flows in the opposite direction to the field. Hence option (B) is correct.

Note:
There are other ways also to induce emf, this is done by either changing the area of the coil, or changing the orientation of the coil. When the area of the loop is increased, the flux through the coil changes which leads to induction of emf.