how does a capacitor filter work in a dc power supply to smooth pulsating dc?

 

A capacitor stores charge in proportion to the voltage and its size by the relation Q=CV. Thus during the time the rectifier is conducting, the capacitor is storing some of the charge as the voltage rises. Then when the rectifier stops conducting, the capacitor releases some of its charge to keep supplying current to the load while the capacitor voltage is being reduced. The difference between the two voltage levels is called the ripple voltage. You can never make this ripple 0V with a passive filter but you can make it arbitrarily low by how large a filter capacitor you use.

 

A Capacitor when impressed with varying high voltage(DC) will store the additional charge and the is supplied by the capacitor to load when the input goes low.Thus the varations across the capacitors are smoothened out.

 

thanks for the help