1. The problem statement, all variables and given/known data A selfinduced emf in a solenoid of inductance L changes in time as E = E.e^-kt. Find the total charge that passes through the solenoid, assuming the charge is finite. 2. Relevant equations E = LdI/dt U = 1/2LI^2 I = dQ/dt 3. The attempt at a solution I'm pretty stumped by this one, honestly. I thought I might have to use I(t) = E/R(1 - e^-Rt/L) somehow. I don't really understand how the emf is changing in time?