Two short magnetic dipoles, each having a magnetic moment of 1 A m2, are placed at points O and P respectively such that their axes are mutually perpendicular and the distance OP is 1 m. The torque experienced by the second magnetic dipole due to the presence of the first is: (in units of 10-7 N m)

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?