Why use capacitors!

[bhsmith]

I've been studying capacitors and I can see how they are useful for AC circuits but I don't understand there uses for DC circuits unless you need a quick discharge like a camera flash.  From what I've read they block DC current, but I see them all the time in schematics of DC circuits and I don't know how they would work if once the voltages are equal the capacitors block the current.  Can anyone help me out with this, it's driving me insane?

[Soeren]

Hi,

Capacitors are used in DC circuits to filter out noise and as current buffers where you have pulsed current draw (caps are effectively lowering the impedance at the point of insert).

[bhsmith]

If my power source is a battery, wouldn't the current be steady.  Wouldn't the cap block the current from flowing once the voltages are equal?

[SmAsH]

No, a capacitor, if placed in parallel will absorb voltage spikes and fill in voltage drops.
If there are none it is as if the cap isn't there. Even if you are using a battery, there can be spikes caused by many things such as external noise or something else like a dc motor running off the battery.

[bhsmith]

Oh, I forgot about using them in parallel.  Well that answers my question.  Thank You!!!  I can go to sleep now.