c Moment Formula: Calculation for a Bar Magnet(a) If a magnet of length l and magnetic moment M gets bent in the form of a semicircular, then its new magnetic SEE moment will be M’ = 2M/π(b) The magnetic moment of a given electron because of its orbital motion is 1μB. But due to its spin motion, it will be μB /2.i.e. Morbital = and Mspin = s Here μB = Bohr magneton(i) The value of Bohr magneton μB = eh / 4πm(ii) μB = 0.93 × 10–23 Amp-m2(c) Other formulae for magnetic moments:(i) M = ni R2(ii) M = eVr/2 = er2ω/2 = er22πf/2 = er2π/T(iii) e/mJ(iv) M = nωB(d) How can we calculate RESULTANT magnetic moment? (i) When two bar MAGNETS are lying mutually perpendicular to each other, thenM = √M12 + M22 = √2mplWhen two coils with a radius of r and carrying current I each, are lying concentrically with their planes at right angles to each other, thenM = √M12 + M22 = √2iπr2 if M1 = M2Illustration: A square loop OABCO of side l carries a current i. Now, find the magnetic moment of the loop.Solution: Magnetic moment of the loop can be written as,M = i (BC x CO), where the letters in bold denote the vectorsBC = -lkThis was our article on magnetic moment formula.