A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moment μ is given by

As revolving charge is equivalent to a current loop, so electric current corresponds to the revolution of electron is I=q  f=q  ×  ω2πBut ω=vR,  where R is radius of circle and v is uniform speed of charged particle. Therefore, I=qv2πRNow, magnetic moment associated with charged particle is given byor      μ=qv2πR  ×  πR2 = 12  qvR