Capacitors do not play an important role in DC circuits because it is impossible for a steady current to flow across a capacitor. If an uncharged capacitor C is connected across the terminals of a battery of voltage V then a transient current flows as the capacitor plates charge up. However, the current stops flowing as soon as the charge Q on the positive plate reaches the value Q=CV. At this point, the electric field between the plates cancels the effect of the electric field generated by the battery, and there is no further movement of charge. Thus, if a capacitor is placed in a DC circuit then, as soon as its plates have charged up, the capacitor effectively behaves like a break in the circuit.
In DC, capacitor once charged, will remain charged forever till conditions remain same and act as open circuit.
In AC, Capacitor has repeated cycles of charging and discharging, hence never an open circuit.
A capacitor works on AC or DC, except at DC it has an infinite impedance. The impedance of a capacitor is -j/(2 pi f C).
as a filter or as a source of electricity in down-cycle? the basic idea is that if you are under DC, the cap is always filled to a constant level and never has a chance to bleed out its charge. nothing more comes in and nothing leaves. it is as if it weren't even there, for practical purposes. It doesn't act as a filter because there is no waveform to attenuate.
But hey, not my expertise.
NOT TRUE !
CAPACITOR CAN BE USED ON BOTH DC AND AC CIRCUITS.
