# An emf self-induced in a solenoid of inductance L changes . . .

1. Oct 31, 2006

An emf self-induced in a solenoid of inductance L changes in time as
E=E_0e^(-kt)
Find the total charge that passes through the solenoid, if the charge is finite. (Use E_0 for 0, k, and L as necessary.)

Now I know that the induced emf is

E_L=-L(dI/dt)
I'm having a hard time on this problem since I'm looking for the charge, and not for the current which I believe I have to determine in the first place. I'm not sure how to exactly find di/dt and then relate it to the charge. Could anyone assist with this please?

2. Oct 31, 2006

I know that I have to take the integral of an equation twice, though I do not know how to incorporate L and the given equation into one really.

3. Oct 31, 2006

### Mindscrape

I don't see any integration, but rather differentiation. They tell you that $$E = E_0 e^{-kt}$$ - this is a given correct? So, what about using chain rule to find $$\frac{di}{dt}$$, which will give you charge?

4. Oct 31, 2006