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## Homework Statement

Imagine that you have a light-bulb that has a resistance of about 10 ohms and that can tolerate a maximum voltage of 3 volts. Imagine that you want to connect this to a charged capacitor large enough to keep the bulb glowing reasonably brightly for more than 10 seconds. Roughly what should the capacitor's capacitance be?

## Homework Equations

V

_{C}(t) = V

_{0}e

^{(-t/RC)}

## The Attempt at a Solution

I feel as if I need another equation for this problem, because I don't have 4 variables to plug in! The starting potential of the capacitor should be 3 volts, right?

So

V

_{C}(t) = (3 volts)e

^{(-10 seconds/(10 ohms)*C)}

So now I have unknowns of C and V

_{C}, and I need to solve for C. Clearly I'm missing something, but I'm not sure what... Can somebody point me in the approximately right direction? Thank you!