Q. A uniform current carrying ring of mass m and radius R is connected by a massless string as shown in diagram. A uniform magnetic field B₀ exists in the region to keep the ring in horizontal position, then the current in the ring is ( length of string)

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A

B

C

D

Solution:

Torque due to magnetic field ...(i)
Torque due to weight about the point where string is connected ...(ii)
If ring remains horizontal, then

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