Very basic questions about capacitors

[G_S]

Hello. I am a beginner in t electronics, and have a very basic question: what are capacitors for? I mean, besides acting as batteries, what is the point of having them in a circuit? Do they save battery power? I have read several tutorial bbut all I can see is that people use them to keep the circuit alive while the batteries are removed. What is the practical usefulness of this?

 

[audioguru2]

A battery voltage remains fairly high as it is used. A capacitor voltage drops quickly at the beginning of powering something then drops less later. So a capacitor cannot be used as a battery unless the current is extremely low.

A resistor feeding a capacitor is a filter and it produces a phase shift. The phase shift produced by a capacitor is the opposite to the phase shift produced by an inductor and together they resonate.