Hi. I have a question concerning the magnetic momentum of a current loop. We know that if we have a circular current loop (a solenoid with N=1), there is a magnetic moment (mu) in the center of the loop given by "mu=S I" (I=current, S =surface enclosed by the loop). So, if there is an external magnetic field B, we can have a torque (tau) given by "tau=mu x B". In order to calculate this, we need to have a magnetic field with its field lines passing through the center of the surface enclosed by the loop. What happens when we have a magnetic field with lines passing thruogh the surface of current loop, but not in the center? Would it be any torque? I guess these questions are linked to the fact that the magnetic momentum "mu" of a current loop is defined only in the center of the surface enclosed by the loop (or not?). Thanks to everyone.