A 40cmX30cm rectangular loop rotates at 130 r/s in a magnetic field of .06 in the direction normal to the axis of rotation. If the loop has 50 turns, determine the induced voltage in the loop. Heres what I did. I used B dot ds. I had my ds being the sides of the rectangle and coswt in the normal direction. I then took the derivative of that. So I multiplied 130*.4*.3*50*.06. The 50 comes from the number of turns. I ended up with an answer of 46.8 sin 130 t. The book has an answer of -54. Since the magnetic field is unchanging, the voltage has to be time-varying.