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## Homework Statement

The power absorbed by the box is ##p(t) = 2.5e^{-4t}W##. Compute the charge and energy delivered to the box for ##0 < t < 250ms##.

An image of the problem: http://gyazo.com/7cb5858f681c3c9db33e20b434c2b782

## Homework Equations

##i = \frac{dq}{dt}##

##q = \int_{-∞}^{t} i dx##

Note that energy over time is the same as work over time.

##\frac{dE}{dt} = p = vi##

##E = \int_{t_1}^{t_2} p dt = \int_{t_1}^{t_2} iv dt##

##v = 50e^{-t}V##

##p = 2.5e^{-4t}W##

##0 < t < 250ms##

## The Attempt at a Solution

The question asks to compute the charge and energy delivered for ##0 < t < 250ms##.

I don't have any current to work with, but I do have power and voltage.

Wouldn't I just integrate ##p(t)## from 0 to 250? That would give me energy.

Integrating ##p(t)/v(t)## from 0 to 250 would give me charge wouldn't it?

Something doesn't feel right. The answers are different.

The answer for the energy is listed as: 395.1mJ

The answer for the charge is listed as: 8.8mC

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