A bar magnet of length 14 cm is placed in the magnetic meridian with its north pole pointing towards geographic north. A neutral point is obtained at an axial distance of 18 cm from the centre of the magnet. If the horizontal component of Earth's magnetic field is BH = 0.4 G, find the magnetic moment of the magnet. (Given: 1 G = 10-4 T)

Two similar circular coils, each of radius R, are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2I respectively. The resultant magnetic field of induction at the common centre will be (μ0 = Permeability of vacuum):

Two long parallel conductors separated by a distance 'd' carry currents I1 and I2 in the same direction. They exert an attractive force 'F' on each other per unit length. If the current in one of them is doubled and its direction is reversed, and the distance between them is increased to 3d, what will be the new value of the force between them?