Capacitors are devices which store electric charge.
They consist of two conducting objects placed near one another but not touching. Most capacitors consist of a pair of parallel plates rolled into a cylinder with insulation between the two plates. If voltage is applied to a capacitor, it becomes charged quickly. This charge is in the form of a negative charge acquired by one plate, with an equal amount of positive charge acquired by the other plate. In other words, Q is directly proportional to V according to the constant of proportionality, C .