Question

In the figure a charged sphere of mass m and charge q starts sliding from rest on a vertical fixed circular track of radius R from the position shown. There exists a uniform and constant horizontal magnetic field of induction B. The maximum force exerted by the track on the sphere is

• A. mg
• B. 3mg – qB
• C. 3mg + qB
• D. mg – qB

Answer 1

Answer: (B)

3mg – qB

Answer 2

F_m = qvB, and directed radially inward.

N - mg sin θ + qvB = ⇒ N

=

Hence at θ = π/2

.

Hence (2) is correct