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

Options

A. `Q omega R^(2)`
B. `1//2 Q omega R^(2)`
C. `Q omega^(2) R`
D. `1//2 Q omega^(2) R`

Answer

B

Explanation

`M = IA `
`I = (Q omega)/(2pi) , A = pi R^(2)`
`m = (Q omega)/(2pi) xx pi R^ (2) = (1)/(2) Q omega R^(2)`