Q.

A particle of charge q and mass m moves in a circular orbit of radius r with an angular speed ω. The ratio of the magnitude of its magnetic moment to that of its angular momentum depends on                 [2000]

1 ω and q  
2 ω, q and m  
3 q and m  
4 ω and m  

Ans.

(3)

The angular momentum of the particle

L=mvr=mr2ω where ω=2πn          [∵v=rω]

∴  Frequency n=ω2π; Further, i=qt=q×n=ωq2π

Magnetic moment, M=iA=ωq2π×πr2⇒  M=ωqr22

∴  ML=ωqr22mr2ω=q2m