Question

Tow magnetic inductions, due to abar magnet at two points distant 0.10 m and 0.20 m respectively form the center are in the ratio 12.5 to 1. find the distance between the poles of the magnet

Answer 1

Magnetic field due to a bar magnet of magnetic dipole moment M at a distance r from it in a direction θ with its magnetic moment is given by B = (μ0/(4π)). (M/r3). (3cos2θ + 1)½. μ0/(4π) = 10−7 T.m/A, M = 2 A m2,  r = 1 m θ = 60° Substituting all the above values in the expression for B, we get B = (10−7 T.m/A) x (2 A m2 / 1 m3 ) (3/4 + 1)½.    = √7  x  10−7  T.