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new_id_7
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Homework Statement
I am trying to understand how to get the voltages Va and Vc in the following circuit.
It is assumed the circuit has been like this for a very long time.
Homework Equations
Kirchoff's voltage law
The Attempt at a Solution
So I know that the capacitor acts like an open circuit to DC. The current through the resistor is obviously 0, so the voltage across the resistor is also 0.
I redraw it like this ( easier to visualize for me ).
Now, I have the answer from my book to be that Va is 0 and Vc is 80. This allows KVL to work.
How do you know that Va is not 80 and Vc is 0? To find the voltage between nodes "a" and "b" I usually do Voltage @ a - Voltage @ b (using correct signs). Doing this between the top of the 80V source, and the top of the resistor gives: Va = 80 - 0 = 80. If I do this at the bottom, I get Vc = 0 - (-80) = 80. Obviously this is wrong because KVL won't hold.
Thanks for any help