1. The problem statement, all variables and given/known data A magnetic flux of 400 micro-webers passing through a coil of 1200 turns is reversed in 0.1 sec. Calculate the average value of the e.m.f. induced in the coil. (Hint use Faraday's Law) 2. Relevant equations 3. The attempt at a solution So I know that phi = F/R Wb phi is flux F is magnetomotive force MMF R is reluctance I also know that F = N I F is the MMF N is the number of turns in the coil I is the current in each turn I now that faradays law is E = - N * d[phi_B]/dt Where E is the electromotive force (EMF) N is the number of turns in each coil phi_B is the magnetic flux through a single loop Given: phi_B = 400 micro Wb N = 1200 turns t = 0.1 s solve for E I don't see how to solve this problem. I know phi_B but not the derivative of it as a function of time. I also don't know the current. Any help would be greatly appreciated.