Capacitors physics question...Help?

Question

suppose you have a 9.00 V battery, a 2.00uF capacitor, and a 7.40 uF capacitor. Find the charge and energy stored if the capacitors are connected to the battery in series. Do the same for a parallel connection.

Answer 1

Capacitors in series have the same charge.  If you combine the capacitors in series, you get a single capacitor with capacitance Ctot = 1/(1/2 + 1/7.40) uF.  The charge is the same for capacitors in series, so solve for Q using Q=CV (where V is just the EMF from the battery). Energy stored is given by the function U=(1/2)CV^2

Capacitors in parallel have the same voltage.  If you combine the capacitors in parallel, you get a single capacitor with capacitance Ctot = 9.40 uF.  The voltage across each is the EMF of the battery (think of Kirchhoff's loop rule.  Any loop you take around the circuit will take you across the battery and exactly one of the two resistors, so the EMF of each resistor is just the EMF of the battery).  You have their respective capacitances and their voltages, so just solve for Q in the Q=CV equation; solve for power just like you did above.

Hope this helps!