Working Out Capacitance?

Question

How would i go about answering these, is there website that could help?

A 4µf capacitor is connected in parallel with a 6µf capacitor. This arrangement is then connected in series with a 10µf capacitor. A supply p.d. of 250V is connected across the circuit.
Find
a)The equivalent capacitance of the circuit
b)The voltage Across the 10µf capacitor
c)The charge on Each capacitor

Cheers

Answer 1

Capacitor combinations are analogous to resistor combinations, except series and parallel formulas are reversed. Capacitors in parallel: C1 + C2; capacitors in series: 1/C = 1/C1 + 1/C2.

First find the combined value of the parallel capacitors and replace with a single capacitor of that value (Cp). Then use the series formula with that capacitor and the 10µF capacitor to get the resulting equivalent capacitance of the circuit.

The voltage across each capacitor will divide inversely as the value of the capacitor. If V1 is the voltage across the 10µF capacitor, then V-V1 is the voltage across Cp; also
V1/10µF = (V-V1)/Cp. From these formulas you can get V1.

The charge on each capacitor is the voltage across it times its capacitance. Therefore for the 10µF cap, it is V1*10µF; for the others, each has a voltage V-V1 across it.

Take care of following the units: 1 coul = 1V * 1farad.
1µF = 10^-6 farad.