Capacitors in Series and in Parallel

In summary, you can't replace the capacitors in the leftmost triple without breaking the branches, which changes the circuit.
  • #1
sweetreason
20
0
I am trying to solve the problem another poster asked about in

https://www.physicsforums.com/showthread.php?t=382491.

I realize how the problem is supposed to be solved, and that you have to start with the rightmost 3 capacitors because none of the other capacitors are in series or in parallel, but I don't understand why this last fact is the case. Why can't you for instance, find the equivalent capacitor for the two leftmost triples (C1, C2, C1) individually [as these seem to me to each form a self-contained series] and the rightmost (C1, C1, C1) separately, which would leave you with three capacitors in parallel?

Thanks!
 
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  • #2
The leftmost triple has branches connecting to it on either side of C2, so you can't treat C1-C2-C1 as being purely in series, independent of the rest of the circuit. But the three C1s in the rightmost triple are purely in series, so you can replace them by their equivalent.
 
  • #3
Hi Doc Al,

Thanks for your reply. I'm still not quite sure I understand -- what is it about being on the far right that makes those three capacitors independent of the rest of the circuit? I would have actually thought that that being on the leftmost end would make you the most independent, since charge flows to those capacitors directly without intermediary. You said that there are branches connecting the leftmost triple on either side of C2, but I'm not sure why this is fundamentally a different kind of connection than the branches at points c and d which connect the rightmost series with the rest of the circuit.

Thanks!

sweetreason
 
  • #4
sweetreason said:
You said that there are branches connecting the leftmost triple on either side of C2, but I'm not sure why this is fundamentally a different kind of connection than the branches at points c and d which connect the rightmost series with the rest of the circuit.
For the rightmost series, points c and d are outside the triple (on the ends), so there's no problem replacing what's between c and d with its equivalent. But on the leftmost triple the branches are in the middle of the triple. You cannot replace those three with a single equivalent without breaking the branches somehow (and thus changing the circuit).
 
  • #5
Okay, I think I can work with that. Thanks a lot!
 

Related to Capacitors in Series and in Parallel

1. What is the difference between capacitors in series and in parallel?

In series, capacitors are connected end-to-end, while in parallel, they are connected side-by-side. In series, the total capacitance is less than the capacitance of individual capacitors, while in parallel, the total capacitance is greater than the capacitance of individual capacitors.

2. How does the voltage drop across capacitors in series and in parallel differ?

In series, the voltage drop across each capacitor is different and adds up to the total voltage, while in parallel, the voltage drop across each capacitor is the same and equal to the total voltage.

3. What happens to the total capacitance when capacitors are connected in series and in parallel?

In series, the total capacitance decreases, while in parallel, the total capacitance increases. This is due to the relationship between capacitance and voltage in these configurations.

4. How do capacitors in series and in parallel affect the total charge stored?

In series, the total charge stored is the same on each capacitor, while in parallel, the total charge stored is divided among the capacitors based on their individual capacitances.

5. What are the advantages and disadvantages of using capacitors in series and in parallel?

The advantage of using capacitors in series is that it allows for precise control of capacitance and voltage, while the disadvantage is that it decreases the overall capacitance. The advantage of using capacitors in parallel is that it increases the overall capacitance, while the disadvantage is that it can be more difficult to control the individual voltages across each capacitor.

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