Explain the term induced emf?
Ans :-
Whenever magnetic flux linked with the coil changes, an emf is always induced in it . This change in magnetic flux can be brought in the following two ways……………..
(a) If the conductor is moved in a stationary magnetic field in such a way that the magnetic flux linked with it changes in magnitude. Then, the emf induced in this way is called dynamically induced emf.
(b) If the conductor is stationary and the magnetic field is moving or changing. The emf induced in this way is called statically induced emf. It is so called because the emf induced in the conductor which is stationary .
A statically induced emf is further sub-divided into……..
(i) Self-induced emf & (ii) Mutually-induced emf
How an induced emf is produced dynamically on a uniform magnetic field, explain ?
Ans :-
If a conductor is moved in a uniform ( stationary ) magnetic field in such a way that the magnetic flux linked with it changes in magnitude, then the induced emf is known as dynamically induced emf .
Dynamically induced emf is illustrated with the help of following figure..... 
Consider a single conductor A of length L meters and let, it is moving at right angles to a uniform magnetic field of flux density B wb/m2 with a velocity V m/s as shown in the figure. Suppose the conductor moves through a small distance dx in time dt. Then area swept by the conductor is =?(L) × (dx) m2
So magnetic flux cut, (dØ) = Flux density × area swept
= BLdx wb
Change in flux ( dØ ) = BLdx wb
Time taken = dt
According to Faraday’s law of electromagnetic induction, emf induced e in the conductor (A) is equal to rate of change of flux linkages.
e = Nd Ø/ dt
e = BLdx/ dt =BL( dx/ dt) [ where, N = 1 & dx /dt = v ]
e = BLv volts
What is self induced emf ?
Ans :-
When a current is flow through a coil, a magnetic field is established through the coil itself. If the current in the coil changes, the magnetic field ( flux ) linked with the coil also changes and an emf is induced in the coil. This emf is known as self-induced emf. The magnitude of this self induced emf is equal to the rate of change of magnetic flux linked with the coil, i.e.,
e = N(d ∅/ dt) volts
The direction of self induced emf can be found by Lenz’s law. According to this law the induced current flows in such a direction that the action of magnetic field set up by it tends to oppose the very cause which produces it.
It should be noted here that self induced emf exist in the coil when the current in the coil changes. When current in the coil steady or constant the magnetic field also becomes constant and there will be no existence of self induced emf in the coil.
It should be noted here that self induced emf exist in the coil when the current in the coil changes. When current in the coil steady or constant the magnetic field also becomes constant and there will be no existence of self induced emf in the coil.
What is mutually induced emf ?
Ans :-
The emf induced in a coil due to the changing current in the neighbouring coil is called mutually induced emf.
Consider two coils A & B placed adjacent to each other as shown in the above figure. A part of the magnetic flux produced by coil A due to the changing current links with coil B. As the current in the coil A changes, flux linked with coil B is also changes. Hence a mutually induced emf is produced in coil B.
The magnitude of mutually induced emf is given by Faraday’s law and the direction of mutually induced is given by Lenz’s law.
The mutually induced emf in coil B exist as long as the change of current in coil A continues. If the current in coil A becomes constant, the mutual flux also becomes steady and so no mutually induced emf in coil B.
