# Capacitors in series questions

1. Sep 17, 2006

### ulfric

The circuit is a series of 3 capacitors with a battery.
C1 = C
C2 = 2C
C3 = 3C

How do you find the voltage across the first capacitor in a series of 3?

How do you find the charge Q on the first capacitor?

How do you find the equivalent capacitance Ceq for this combination of capacitors in series?

I had these questions on a test and know the answers but not how to arrive at them. I am usually quick on the uptake but teaching this basic stuff adequately is apparently beneath my professor and the text is terrible! (stay away from Young & Geller!)

Thanks for any help you can provide.

2. Sep 17, 2006

### SGT

The equivalent capacitance of a series of n capacitors is done by the expression:
$$\frac{1}{C_{eq}}=\sum_{k=1}^n \frac{1}{C_k}$$
The charge in all capacitors is the same.
Charge, voltage and capacitance are related by:
$$q = CV$$