where μ is the dipole moment of the loop,

and B is an external magnetic field.

Q1 Is it true that we can only write the Torque due to an external magnetic field in this form if and only iff B is a constant? What happens, say, if B = B * x (in the z-direction) where x is a variable, is it still possible to write Torque in this form, where μ is a constant.

Q2 Why is it that Force = 0 but Torque is not = 0 when the external magnetic field is constant?

Cheers guys