A bar magnet is 10 ~cm long is kept with its north (N) -pole pointing north. A neutral point is formed at a distance of 15 ~cm from each pole. Given the horizontal component of earth's field is 0.4 Gauss, the pole strength of the magnet is

Step-by-step solution

aligned & Length of magnet =10 ~cm =10 10⁻² ~m , & r=15 10⁻² ~m aligned O P= 225-25 = 200 ~cm Since, at the neutral point, magnetic field due to the magnet is equal to B_H gathered B_H= ₀ 4 M (O P^2+A O^2 )^ 3 / 2 0.4 10⁻⁴=10⁻⁷ M (200 10⁻⁴+25 10⁻⁴ )^ 3 / 2 0.4 10⁻⁴ 10⁻⁷ (225 10⁻⁴ )^ 3 / 2 =M 0.4 10^3 10⁻⁶(225)^ 3 / 2 =M M=1.35 ~A - m gathered