1. A small current loop of area A=0.0007m2 and moment of inertia I=6.6e-07kgm2 carries a current i=0.0045A with its magnetic moment perpendicular to the Earth's magnetic field. The magnitude of the Earth's field is B=4.2e-05T. What is the magnitude of the net torque T on the loop? 2. Relevant equations (1) τ(torque) = I([itex]\alpha[/itex] (2) τ = μ X B (3) torque = current*area*B 3. The attempt at a solution I'm not sure where to begin. I would plug numbers into the third equation but it doesn't make sense of where the moment of inertia comes into play...help? edit: Okay so I did use (3) to find the right answer. I'm not sure how this works though. so in my drawing i just have a square loop and the question says it is perpendicular to Earth's B field, I thought perpendicular meant they cancel out?