What Determines the Torque and Magnetic Moment in Magnetic Systems?

[pardesi]

when we write $\vec \tau=[\vec \mu, \vec B]$
what is the point or the line about which we are calcuating the torque
Also what is the magnetic moment's expression for a surface current and volume current distribution?

 

[Shooting Star]

The moment of magnetic dipole is independent of the origin. The torque is a pure couple and so it too is independent of the choice of origin.