(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

What is the voltage across a capacitor after a time of two constants when charging from zero voltage. When discharging from a fully charged condition?

2. Relevant equations

V_{Capacitor}= V_{Battery}(1 - e^{-t/2T})

V_{Capacitor}= V_{Maximum}* e^{-t/2T}

3. The attempt at a solution

I'm confused at how to start. I can do the algebra...

Charging from zero voltage - so would I set V_{Maximum}to 0? Wouldn't I need to know V_{Battery}? That wouldn't make sense to me. If I can get an idea of how to approach this problem, I should be able to solve it no problem. Thanks!

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1. The problem statement, all variables and given/known data

With V = V_{o}*e^{-t/RC}, it mathematically takes an infinite time for a capacitor in an RC circuit to discharge. Practically, how many time constants does it take for a capacitor to discharge to less than 1% of its initial voltage?

2. Relevant equations

V = V_{o}*e^{-t/RC}

3. The attempt at a solution

0.01*V_{o}= V_{o}*e^{-t/RC}

0.01 = e^{-t/RC}

100 = e^{t/RC}

ln(100) = t/RC

2*ln(10)*RC = t

So, I'm saying that it takes approximately 4.61 time constants.

Would this be correct? Thanks!

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# Homework Help: RC Circuit - Post-Lab Questions

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