how the capacitor work in the dc supply?

Answer 1

Capacitors are used in electrical circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals and this makes them useful in electronic filters.

Electrons cannot easily pass directly across the dielectric from one plate of the capacitor to the other as the dielectric is carefully chosen so that it is a good insulator. When there is a current through a capacitor, electrons accumulate on one plate and electrons are removed from the other plate. This process is commonly called 'charging' the capacitor -- even though the capacitor is at all times electrically neutral. In fact, the current through the capacitor results in the separation of electric charge, rather than the accumulation of electric charge. This separation of charge causes an electric field to develop between the plates of the capacitor giving rise to voltage across the plates.

The capacitors act as a local reserve for the DC power source, and bypass AC currents from the power supply.

Answer 2

aservtech is basically correct. The capacitors in a DC supply act as filters to remove ripple from the output voltage. In the absence of a capacitor at the output, the supply's output voltage would resemble a half-sine wave (one every cycle for half-wave and two per cycle for full-wave rectification). The capacitor stores charge during the rising voltage part of the sine wave, and discharges when the input voltage falls below the voltage built up in the capacitor. The voltage thus become more uniform and more like true DC.

Answer 3

in a dc supplied circuit, capacitor tends to open-circuit.. it only works as explained above in an ac supplied circuit.

Answer 4

the Large caps it a DC suply are the filters they act like highly efficent batterys to stableize DC Voltage and Reduce AC Ripple / line noise. Caps can also be looked at as Water Towers in plumbing.