1. The problem statement, all variables and given/known data a single loop is placed deep within a 4 meter long solenoid having a total number of turns equal to 40000. the loop has an area od 0.01m^2 and it carries a current of 20 ampere. the loop is oriented so that the torque on the loop is a maximum with a magnitude of pi*10^-4 newton meters. what is the current in the solenoid? 2. Relevant equations magnetic dipole moment, mu = NIA where N is number of turns, I is current, A is area torque, tau = mu X B where X indicates cross product, B is magnetic field magnetic field, B = mu_0/4pi[integral(IdL/r^2)] where mu_0 is constant = 4pi*10^-7, dL is change in length, r is radius/distance, I is current 3. The attempt at a solution mu = NIA mu = (40000)(20)(0.01) mu = 8000 tau = mu X B pi*10^-4 = 8000sin(90) ---> max torque so theta = 90 degrees pi*10^-4/8000 = B B = 3.93*10^-8 Teslas area of circle = pi(r^2) sqrt[0.01/pi] = r r = 0.056 m B = mu_0/4pi[integral(IdL/r^2)] 3.93*10^-8 = (10^-7(4)I)/(0.056^2) I = ((3.93*10^-8)(0.056^2))/(4*10^-7) I = 3.075*10^-4 ampere correct approach? correct answer?