# Charge from current

1. Aug 24, 2006

### Valhalla

In this problem assume that current is linearly proportional to time. The intial condition at time 0 is 5A. At time 4 hours the current is 1A. What is the total charge that flows through this circuit?

$$t_0=0$$
$$i_0=5A$$
$$t_f=14400s$$
$$i_f=1A$$

$$\frac{i_f-i_0}{t_f-t_0} =\frac{-4A}{14400}$$

$$q=\int_{0}^{14400}(\frac{-1A}{3600}t+5)dt$$

$$q= \left[\frac{-1}{7200}t^2+5t\right]_{0}^{14400}$$

$$q= 43200C$$

That seems like a whole lot of charge. I know it is a long period of time. Can anyone see anything wrong with this?

Last edited: Aug 24, 2006
2. Aug 24, 2006

### quasar987

1A is a very large current too. It looks fine to me.