Problem: A hundred turns of insulated copper wire are wrapped around an iron cylinder of cross-sectional area 1x10^-3 sqr. m and are connected to a resistor. The total resistance in the circuit is 10 ohms. If the longitudinal magnetic field in the iron changes from 1.0 T in one direction to 1.0 T in the opposite direction, how much charge flows through the circuit. I was wonderin why the direction will affect the magnitude of the charge?