What Is a Capacitor?


Capacitors are composed of two electric plates that are able to store an electric charge in-between them when activated. The electric storage devices range in size and are commonly used in a number of electronic and mechanical devices. They run on equal charge and opposite polarity theories and allow electronic devices to run much longer than they would with a traditional power source. A secondary use for these devices involves them being an electronic filter.


  • In 1745, two capacitors were invented individually at around the same time. The men responsible were Ewald Georg von Kleist of Germany and Pieter van Musschenbroek of the Netherlands. These early capacitors were jars filled with water that were connected to a battery, which delivered an electric charge into them. Benjamin Franklin performed an investigation into these devices and learned that the charge they were able to hold was in the glass of the jars, not the water that filled them. Capacitors were upgraded as time went on, though the function did not change all that much.


  • A capacitor is composed of two basic plates that are each connected to a power source. The plates can be different shapes and sizes, but are of equal size and mass and face each other. Cords run from each plate and connect to each other with a battery in between that feeds them both with electricity. This is the basic setup of a capacitor, and usually it is set inside a metal tube and put into the device that it is storing electricity for.


  • A capacitor works by first powering the two plates that it is composed of. Each plate will have an equal electrical charge, but they will have opposite polarizations. While the power source they are attached to feeds them electricity, no current can flow between them. The electric charge is instead held in the plates themselves. When the power source is cut off, the plates continue to hold their charge, and they are drawn to each by their reverse polarization. Since they cannot move, the electricity flows between them and is stored between the plates. The device that the capacitor is part of can then draw from this extra source of power as it needs to.


  • There are many different types of capacitors out there, most of which are different because of the dielectrics in them. This is the substance that is set between the two plates. Some capacitors that attract a high voltage have nothing but air between them. Others use a solid that could be composed of ceramic, glass, plastic or even paper. The plates are also made of different materials. Some are composed of aluminum, and others or tantalum or other similar metals.


  • Devices that have capacitors need to be handled carefully even when they are not connected to a power source. This is because capacitors are able to hold high voltage charges long after they are removed from their original source of power. They can, therefore, deliver a powerful shock to those people who handle them incorrectly. If you are servicing a device that has a capacitor, carefully read the instructions that come with it as they will be able to tell you how to safely deal with a capacitor.

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