The torque on a current loop is zero if the angel between the positive normal and the magnetic field is either θ = 0 or θ = 180°. In which of the two orientations, the equilibrium is stable?

Question

Philoid · Accepted Answer

Formula used: Potential energy is given by

Where m is magnetic moment

B is magnetic field

Let is take B=0.1T, m = A m �

If θ is zero, then

If θ=180 then

If energy is minimum, then system will be more stable. If energy is increase, then the system will loose it’s stability. For θ=0 the energy is minimum and the equilibrium will stable. For θ=180 the energy is maximum and equilibrium will unstable.