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For a charging circuit, the emf supplied by the battery is 200 V, R = [tex]2*10^5\omega[/tex] and C =[tex] 50 \mu F[/tex]. Find:

a) the time taken for the charge to rise to 90% of the final value

b) the energy stored in the capacitor at t=RC

c) the power loss in R at t=RC

I've worked out a). That was simple enough. However when it comes to b) and c) I'm having problems.

For b) I want to use that [tex]E = \frac{CV^2}{2}[/tex], or one of its rearrangements (most probably the [tex]\frac{Q^2}{2C}[/tex] version), however whilst I can find a value for Q in terms of [tex]Q_{0}[/tex], this still leaves me with an unknown in the answer ([tex]Q_{0}[/tex]).

And for c) I have no idea whatsoever - nowhere in my notes or text book, does it say anything about the energy or power in an RC circuit.

Any hints (or blatent worked answers ) would be much appreciated!

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# Homework Help: Energy in a capacitor in an RC circuit.

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