What is the potential difference Vad-Vac?

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The discussion focuses on calculating the potential difference Vcd in a circuit with initially uncharged capacitors connected to a 210 V source. The equivalent capacitance of the series was determined to be 4 x 10^-6 F, leading to a charge calculation of 8.4 x 10^-4 C. The user initially attempted to find the voltages Vad and Vac using the formula V=Q/C but later realized that each series had half the charge. Ultimately, the calculated values were Vad=140V and Vac=70V, resulting in a potential difference of Vad-Vac=70V. The problem was successfully solved by correctly applying the principles of capacitance and charge distribution.
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1. The problem statement
The capacitors in the figure are initially uncharged and are connected, as in the diagram, with switch S open. The applied potential difference is Vab = + 210 V.

What is the potential difference Vcd?

YF-24-60.jpg


Homework Equations


(series) 1/C = 1/c1 + 1/c2 + ...
(parallel) C = c1 + c2 + ...
C=Q/V

The Attempt at a Solution


Trying to find Vcd:
I first found the equivalent capacitance of the series, which is 4*10-6 F. I calculated the charge on the capacitors using Q = CV, which was 8.4*10-4. Then, I tried to find Vad and Vac by using V=Q/C. I don't think this is the right way to do this problem though.
 
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That looks like the way to do it as far as you went.
 
Ah, I figured it out. The upper and lower series each have half the value of the charge that I calculated. Then using V=QC, Vad=140V and Vac=70V, so Vad-Vac=70V.
 

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