A short bar magnet with its north pole facing north forms a neutral point at P in the horizontal plane. If the magnet is rotated by 90∘ in the horizontal plane, the net magnetic induction at P is (Horizontal component of earth’s magnetic field = BH )
Finally:
Point P comes on axial line of the magnet and at P, net magnetic field
B=√B2a+B2H
=√(2Be)2+(BH)2=√(2BH)2+B2H=√5BH.