How Does a Capacitor Work?

By Joshua Duvauchelle


An electronic capacitor is an important component in electrical devices. A capacitor is considered a "passive" device because it does not actively affect electrical currents or other electrical components. Instead, capacitors store electrical energy between electrical conductors. The numbers printed on the capacitor refers to the amount of current it can passively hold.

Uses of Capacitors

Capacitors help regulate electrical current. While capacitors allow alternating currents, a steady flow of electrical current fills up the storage ability of the capacitor and prevents any further current from flowing through. Thus, capacitors effectively smooth out electrical currents and ensure a steady current for the entire electrical network.

How a Capacitor Works

An electrical capacitor is made of two small conductive plates separated by what is called a dielectric, which effectively insulates the two plates and stops any current from being transferred between the plates themselves. Instead, the two plates are connected through a circuit. When the circuit is taken out, the plates store the electrical current because it can't flow between the plates. The way a capacitor works is like a water storage tank with a shut-off valve if it gets too full. As electrical current enters the capacitor, the capacitor lets it pass through unaffected. However, the more current flows into the capacitor, the quicker it "fills." This then triggers the capacitor's shut-off mechanism, preventing electrical current from exiting and redirecting the flow to a grounding current.

Types of Capacitors

The functioning and effectiveness of electrical capacitors depends largely on the type of material used to construct the dielectric between the capacitor plates. Common material used to construct the dialectic include paper, plastic, glass, metals (such as aluminum) and ceramics. All types of material suffer from aging, which reduces their ability to function properly over time. Thus, capacitors often need to be replaced if used continuously.