Question

A ring of radius `R`, made of an insulating material carries a charge `Q` uniformly distributed on it. If the ring rotates about the axis passing through its centre and normal to plane of the ring with constant angular speed `omega`, then the magnitude moment of the ring is
A. `QomegaR^(2)`
B. `(1)/(2)QomegaR^(2)`
C. `Qomega^(2)R`
D. `(1)/(2)Qomega^(2)R`

Answer 1

Correct Answer - B
`M=iA=ixxpiR^(2)` also `i=(Qomega)/(2pi)implies(1)/(2)QomegaR^(2)`