Question

Two particles , each of mass ` m` and charge `q`, are attached to the two ends of a light rigid rod of length ` 2 R` . The rod is rotated at constant angular speed about a perpendicular axis passing through its centre. The ratio of the magnitudes of the magnetic moment of the system and its angular momentum about the centre of the rod is
A. `q//2m`
B. `q//m`
C. `2q//m`
D. `q//pim`

Answer 1

Correct Answer - a
Current, i=(frequency) (charge)
`=(omega)/(2pi) (2q) =(qomega)/pi`

Magnetic moment,
`M=(I)(A)=(qomega)/(pi)(piR^2)=(qomegaR^2)`
Angular momentum, `L=2Iomega=2(mR^2)omega`
`M/L=(qomegaR^2)/(2(mR^2)omega) =q/(2m)`