Friday

April 25, 2014

April 25, 2014

Posted by **Lanise** on Wednesday, February 10, 2010 at 11:02pm.

Find the time constant for the circuit.

Find the percentage of the circuit's final voltage after 3.9 s .

Vc/Vi= %

- College physics -
**drwls**, Thursday, February 11, 2010 at 1:01amThe voltage across the capacitor is

Vi * [1 - e^-(t/RC)]

in this type of circuit. Vi is the power supply voltage. RC is the time constant.

The final voltage is Vi.

When t = RC (the time constant), the voltage is

Vc = Vi*[1 - e^-1] = 0.632 Vi

When t = 1.5 s,

0.64 Vi = Vs * [1 - e^(-t/RC)]

e^(-t/RC)= 0.36

t/RC = 1.02

RC = 1.5/1.02 = 1.47 seconds

That is the time constant.

After 3.9 s

Vc = Vi* [1 - e^(-3.9/1.47)]

= 0.930 Vi

Unless you show some work on future posts here, I will not be assisting you again. Perhaps someone else will.

Vc = Vi* [1 - e^(-3.9/1.47)]

= 0.930 Vi

**Related Questions**

Physics!! Help!!!!! - The time dependence of voltage across a discharging ...

physics-RC Circuit - We had to do a RC Circuit experiment in the lab one step in...

physics - In the circuit below, at time t = 0, the switch is closed, causing the...

Physics- Repost (Answer did not make sense) - In the circuit below, at time t...

Physics - A circuit with a capacitor took .128s to discharge from its max charge...

physics - An RC circuit contains a 3.9 kΩ resistor and a 5 µF capacitor. ...

Physics - A circuit with a capacitor took .138s to discharge from its max charge...

Physics circuit help please! - Hi all. I posted earlier but I'm still stuck on ...

Physics - In the following circuit R_1=3 Ohm, R_2=10 Ohm, C=0.003 Farad, V=5 ...

Physics help please! - Hi all. I posted earlier but I'm still stuck on part of ...