Capacitors in Parallel

fact
When two capacitors are in parallel we can replace them with a single equivalent capacitor whose capacitance is given by: $$C_{eq} = C_1 + C_2$$
fact
Adding capacitors in parallel increases the equivalent capacitance.
fact
If three or more capacitors are in parallel we reduce them two at a time just like with resistors.
fact
Capacitors in parallel have the same voltage across them which means the charge on each capacitor is determined by its capacitance and the voltage across them all: $$Q_1 = C_1 \times V$$
example

Find the charge on capacitor $$C_2$$ in the circuit below.

We can see that the voltage across both $$C_1$$ and $$C_2$$ is 10V since they're in parallel. So we can just apply our usual formula to find charge: $$Q = C V$$ where $$Q$$ is charge, $$C$$ is capacitance and $$V$$ is voltage. So $$Q = 10\mu$$F$$\times 10$$V$$= 100\mu$$C of charge.
practice problems