1. The problem statement, all variables and given/known data Starting from the Lorentz force law, in the form of Fmag = ∫ I (d× B), show that the torque on any steady current distribution (not just a square loop) in a uniform field B is m × B. 2. Relevant equations I looked at the solution I found in this thread here, but I don't understand the step after you take the derivative of both sides of the torque equation. Why would you use that method in the next step, and how? Where did it come from? I have Griffiths 4ed. 3. The attempt at a solution This is all I know how to do.