How Capacitors Work?
Details of the various parts in an electrical circuit have been explained in many ways, some simple and some too complex for the average student. But explaining how capacitors work has been reduced to rather simple terms. If we view a capacitor as similar to a tiny battery or as a storage tank we are well on our way to understanding what part the capacitor plays in the circuit.
The name of this item is descriptive. A capacitor has a capacity; it holds electrical energy. A battery does this too, but the capacitor is actually a bit less complicated. While a battery can actually “make” new electrons because of its chemical process, a capacitor can only store the electrons that enter it from somewhere else in the circuit.
A capacitor is made up of two plates that are kept separate by a substance that does not conduct electricity. The plates are connected to two terminals that provide for “communicating” with the rest of the electrical circuit. The tiny plates and terminals must be made of a conducting metal substance, while the separating substance (often called the “dielectric”) is ceramic, porcelain, Teflon and so on.
Capacitors are used in various ways, with some of them designed for high-frequency circuits. Others are made specifically to handle larger amounts of voltage. Capacitors of various sizes and designs are used to tune radios, in clocks and electronic counting devices, in sensitive medical equipment and even in cars and electric vehicles.
We mentioned earlier that a battery is able to produce new electrons because of an internal chemical process, while a capacitor can only store the electrical energy. The battery and the capacitor can work together quite well. Electrons from the battery enter the capacitor from the “negative” terminal of the battery; the capacitor holds the energy and gives up electrons to the “positive” terminal of the battery. When fully “charged” the capacitor has the same voltage as the battery it is connected to.
In a simple circuit that includes a light bulb, a battery or other source and a capacitor, the battery sends its electrons out along a wire that is connected to the bulb, which lights up. But the capacitor also receives electrons and eventually reaches its full charge or capacity. One this level is reached, electrons stop flowing freely and the bulb won’t be brightly lit. If there is not battery in the circuit, the electrical energy stored in the capacitor will flow through the wire and the bulb until the capacitor is “empty.” In this simple example, the capacitor is controlling the electrical energy through the circuit.
One of the more recent uses for tiny capacitors is in touch-screen electronic devices. The screen is charged and when a finger touches it, the finger becomes part of a circuit and the voltage at that location is reduced. The computing device connected to the screen receives this voltage information and its location. This is what makes a touch screen useful. Capacitors allow for very quick discharge of electrical energy stored, making them efficient in electronic devices.