Modelling the Charging of a Capacitor

Thread Starter

Sci

Joined Jan 21, 2005
8
I consulted some text books, which gave me what I attached as a screenshot, for dv/dt of a capacitor from the time it is just to be about charged. To cut a long story short, I'm suppose to model it using the analytical equation and Euler's method. However the voltage DE I got from the text book itsn't working out. It says:

(dv/dt) = (v - Vs) / RC,
where v is the voltage across the cap, and Vs is the applied voltage. Using this equation makes me end up with a neg, or just wrong voltage as opposed to the corrent analytical equation of

v = Vs (1 - e^(-t/RC) )

What's the proper DE?
 

hgmjr

Joined Jan 28, 2005
9,029
Is it possible that you overlooked the negative sign in the expression shown in your screenshot.

It reads dv/dt = - (v-Vs)/RC. This is equal to dv/dt = (Vs-v)/RC.

Hope this help?

Good Luck.
 
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