Question

Two charges of same magnitude move in two circles of radii R, NR and Ry=2R in a regio
of constant uniform magnetic field B..
The work W, and W, done by the magnetic field in the two cases, respectively are such tha
(A) W, = W, = 0 (B) W, > W, (C) W, =W,#0 (D) W, <W,
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Answer 1

Answer :-

In the presence of magnetic field, a moving charge experiences centripetal force given as FB = qvBsin,which acts perpendicular to the velocity vector v......

Since the trajectory of such charge particle is circular, at any instant velocity vector acts along the tangent to the circle......

FB is perpendicualr to v.....

So work done by magnetic Lorentz force FB (due to B) will always be zero......

So correct option is (a) W1 = W2 = 0.....

Hope helps you.....