The relationship between the voltage, charge and capacitance of a capacitor is:
Q = C V
where:
V = voltage across the capacitor (in volts or V)
Q = the charge on the plates of the capacitor (in coulombs or C)
C = the capacitance of the capacitor (in farad or F).
The voltage across the capacitor in the diagram at right is 12V. The capacitance of the capacitor is 3F. Solving for the charge gives:
Q = C V = (3F)(12V) = 36C.