Example from book

Thread Starter


Joined Feb 16, 2014
I always get so confused when two voltage sources are present in a circuit. I never know how they affect the circuit. Am i supposed to combine them into one source by subtracting if they are opposite and adding if the polarity is the same? or am I supposed to use super position and see how each part of the circuit is affected by each one individually?

For this example i get different answers for different methods. If i combine them then i get 24 V source which means the capacitor is at 20 V which is wrong. However using super position i get a total of 32 volts at the capacitor which is right.



Joined Jan 29, 2010
As this homework I will only give you a hint.

As the question states initially the capacitor is fully charged ie: no current flowing into the cap... and the Switch is Open.

You can then see there is only 24V across the resistors connecting the two voltage sources... which gives a current value of:....???

So the Vdrop across the 2K resistor is:... ???

You should post your calculations on the two methods that you used to solve the problem, even though you get incorrect answers, that helps us to see where you are going wrong.