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 – q $B \sqrt { 2 g R }$
• C. 3mg + q
• D. mg – q

Answer 1

Answer: (C)

3mg + q

Answer 2

F_m = q v B (directed radially outward) Q N – mg sin q – q v B = or N = + mg sin q + qvB q = p/2

Hence at q = p/2 N_max = + mg + q

= 3mg + q N_max = 3mg + q