Intuition for Capacitor placed in parrallel or in series

1. Apr 8, 2012

Genericcoder

Hi,

I just want to make sure my intuition is correct for why capacitors add normally when placed in parrallel and add reciprocally when placed in series.

In parrallel they add normally for example

C = C1 + C2 + C3;
Because when placed in parrallel the right hand plate share same Voltage as left hand plate,so the charge aquired would be
CV = C1V + C2V + C3V + C4V;
C = C1 + C2 + C3 + C4;

When you place them in series take 3 capacitors C1,C2,C3 where C1 is on the left C2 is in the middle and C3 is on the right handside.

So when you place them in the circuit C1 will aquire a positive charge so C3 will also aquire negative charge,and since they are neutral their will be also a negative charge on left side of C3,and Positive and negative on the right of C2 and on the left of C2;

So they all share same current:-

Q / C = Q/C1 + Q/C2 + Q/C3;
1/C = 1/C1 + 1/C2 + 1/C3;

I just want to make sure that this intuition is correct.

2. Apr 8, 2012

tiny-tim

Hi Genericcoder!

But your understanding of what happens across the plates is suspect …

the plates of a single capacitor do not "share" a voltage, on the contrary they have a voltage difference

the three right-hand plates do share a voltage, and so do the three left-hand plates, and so the voltage across each capacitor is the same.
This is an odd way of putting it …

a more obvious way is to say that the charges on opposite plates of each capacitor will be equal and opposite, and by conservation of charge so are the charges on adjacent plates of each pair of capacitors.

3. Apr 8, 2012

Genericcoder

Thanks that makes sense :).