Capacitors in Series and Parallel

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Capacitors in Series and Parallel

In series, capacitors will each have the same amount of charge stored on them because the charge from the first one travels to the second one, and so on.

The total charge stored is the charge that was moved from the cell, which equals the charge that arrived at the first capacitor, which equals the charge that arrived at the second, etc...

So, QT = Q1 = Q2 = Q3, etc.

The voltage of the circuit is spread out amongst the capacitors (so that each one only gets a portion of the total).

Capacitors in Series

So from the diagram (and remembering that V=Q/C)

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This is the equation for capacitors in series.

Note: This is similar to resistors in parallel; so combinations of capacitors are the opposite to combinations of resistors!

Two small capacitors in parallel can be thought of as being the same as one big capacitor:

Capacitors in Parallel

There is just as much 'plate' on the left hand side for the charge to flow into in both of these diagrams.

So adding capacitors in parallel will increase the space available to store charge and will therefore increase the capacitance of the combination.

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Capacitors diagram

The pd across each capacitor is the same as the total pd. Let's call it V.

QT = Total charge stored = Q1 + Q2 +Q3

Using Q=VC

VCT = VC1 + VC2 + VC3

As the capacitors or in parallel they each have the same voltage across them, so cancel the V's.

CT = C1 + C2 + C3 for capacitors in parallel.

(This is similar to resistors in series!)