Question

. 21. Determine the motional emf induced in a straight conductor
moving in a uniform magnetic field with constant velocity on
the basis of Lorentz force.
​

Answer 1

Explanation:

Let us consider a straight conductor moving in a uniform and time-independent magnetic field.

The figure shows a rectangular wire PQRS in which the conductor PQ is free to move.

Rod PQ is moved towards the left with a constant velocity v.

PQRS forms closed circuit enclosing an area that changes as PQ moves.

It is placed in a uniform magnetic field B perpendicular to the plane of our system.

Let the length RQ =x and RS =l,

the magnetic flux ϕ

B

enclosed by the loop PQRS

ϕ

B

=Blx

As x is changing with time, the rate of change of flux ϕ

B

will induce an emf given according to Faraday's law of electromagnetic induction :

ϵ=−

dt

dϕ

B

=−

dt

d

(Blx)=−Blv

This induced emf Blv is motional emf.

solution