Two similar coils are kept mutually perpendicular such that their centres coincide. At the centre, find the ratio of the magnetic field due to one coil and the resultant magnetic field through both coils, if the same current is flown Equating Eqs. (i) and (ii) we get m= M C C^2 = M 0.2 100 4.2 10^3 (3 10^8 )^2 ~J m M = 20 4.2 10^3 (3 10^8 )^2 % increase in mass = m M 100= 20 4.2 10^3 (3 10^8 )^2 100=9.3 10⁻¹¹ %