Equivalent Capacitance

[Sami Lakka]

1. The problem statement, all variables and given/known data
What is the equivalent capacitance of the arrangement shown in figure. (Answer is C1)


2. Relevant equations
Cparallel = C1+C2+...Cn
Cseries = 1/(1/C1+1/C2+...+1/Cn)


3. The attempt at a solution

[Andrew Mason]

1. The problem statement, all variables and given/known data
What is the equivalent capacitance of the arrangement shown in figure. (Answer is C1)


2. Relevant equations
Cparallel = C1+C2+...Cn
Cseries = 1/(1/C1+1/C2+...+1/Cn)


3. The attempt at a solutionIt is easier to see what is happening if you change the drawing to a square with 2 C1s on each side in series and a C2 attached across the middle (from points between the C1s).

By the symmetry of the circuit, you can see that there is 0 voltage across the C2 capacitor. So the C2 really does nothing to change the capacitance of the circuit - ie. it never stores charge. So the capacitance is the same as the circuit without C2.

AM