Magnetic moment M=IA=I(πr2)M=(2πreu)(πr2) Given B(πr2)=n(eh) ⇒r2= Bπeh…(2)(∵n=1) And when charge moving in external magnetic field then r=qBmu rv= me B…(3)(∵q=e) Put value from equation (2) and (3) in equation (1) M=(2πrev)(πr2)M=2πe(meB)π(Bπeh)M=2πmeh