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# A circular copper-ring of radius r translates in its plane with a constant velocity v. A uniform magnetic field B exists in the space in a direction perpendicular to the plane of the ring. Consider different pairs of diametrically opposite points on the ring.

(a) Between which pair of points is the emf maximum?

(b) Between which pair of points is the emf minimum?

What is the value of this minimum emf?

Answer :

Given:

Radius of ring =R

Velocity of ring=v

(b) we know that motional emf produced due to a conductor of length l moving with velocity v in a magnetic field B is given by

…. (i)

This value is maximum when length between the points is perpendicular to the velocity of the rod

Thus the emf is the highest between the end points of diameter perpendicular to the velocity and the value of this emf is given by

**Therefore, maximum value of emf is 2BvR**

(c) the value of eqn.(i) is minimum when length between the points is parallel to the velocity of the rod

Thus the emf is lowest between the end points of diameter parallel to the velocity and this value of emf is given by

**Therefore, minimum value of emf is 0**

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