The magnetic torque acting on a loop of magnetic moment M placed in a magnetic field B, is given by τ=M×B. My question is, about which axis does this give the torque about? Is it the instantaneous axis of rotation or the axis about the centre of mass? How do we decide this axis?
Consider the following case of a cylinder(with a planar coil carrying current, plane parallel to inclined plane at the instant, the inclined plane making an angle θ with the horizontal) rolling down an incline such that the net torque on it is 0 , now, in this case will the torque given by M×B be about the point of contact with the inclined plane? Or will it be about the Centre of mass of the cylinder?