- #1
chrisfnet
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Homework Statement
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?
Homework Equations
VCapacitor = VBattery(1 - e-t/2T)
VCapacitor = VMaximum * e-t/2T
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 VMaximum to 0? Wouldn't I need to know VBattery? 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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Homework Statement
With V = Vo*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?
Homework Equations
V = Vo*e-t/RC
The Attempt at a Solution
0.01*Vo = Vo*e-t/RC
0.01 = e-t/RC
100 = et/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!