# Total charge in a circuit

1. Mar 11, 2008

### JFonseka

1. The problem statement, all variables and given/known data
The total charge that has entered a circuit element is q(t)=2(3 − e$$^{-4t}$$) when t≥0 and
q(t)=0 when t<0. Determine the current in this circuit element for t≥0.

2. Relevant equations
Differentiation

3. The attempt at a solution

i(t) = 2(4e$$^{-4t}$$) + 3 - e$$^{-4t}$$

i(t) = 7e$$^{-4t}$$ + 3

However the answer says 8e$$^{-4t}$$

What have I done wrong?

2. Mar 11, 2008

### JFonseka

Nvm. Dumb mistake, just realized. Solved.