Capacitor is the storing device of
current and its unit is farad. Lets check what happens when
the ac voltage is applied to a capacitor.
In electrical and electronic systems, reactance is the opposition of a circuit element to a change in current or voltage, due to that element's inductance or capacitance. When capacitors are connected across a direct current DC supply voltage they become charged to the value of the applied voltage, acting like temporary storage devices and maintain or hold this charge indefinitely as long as the supply voltage is present. Capacitive Reactance in a purely capacitive circuit is the opposition to current flow in AC circuits only which varies with frequencies.
Capacitive Reactance Formula is given by
L is inductance of the circuit,
C is capacitance and
f is the frequency of ac mains.