When an AC voltage is applied to a capacitor, a voltage is created across the plates and charge builds up. The voltage created opposes the applied voltage and limits current flow. In a sense, like an inductor resists changes in current, a capacitor resists changes in voltage.

And this opposition, reactance, is also defined for a capacitor as the capacitive reactance , also measured in ohms just like its inductive counterpart.

This capacitive reactance is also dependent on the frequency, with from which we similarly get that This derivation isn't important, but we end this page too by two other very important conclusions