Hi ,power is the product of current and the resistance that is P=I^2*R
But ,in capacitor at the first positive half cycle it will charge the positive charge ,And the next negative half cycle the capacitor charges negative charge . so there is no net energy in the capacitor.
if the frequency is different the capacitor may be heat.
the capacity in farad means it is the time to charge one cycle .
The equation given by mister_rf shows the relationships among energy (W), voltage (V), and capacitance (C). Power is defined as the rate of change of energy. So the instantaneous power involved in charging or discharging a capacitor is the product of the instantaneous voltage (v) and the instantaneous current (i).