Explain the working of a capacitor

timer Asked: May 16th, 2014
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Question Description

Explain the working of a capacitor 

Tutor Answer

School: Rice University


A capacitor is an electronic device that is used to store electrical energy. They are only used to store the electrons and they are not capable of producing them.

Invention of the Capacitor

There are many stories behind the invention of the capacitor. A German scientist named Ewald Georg von Kleist was known to invent the capacitor in November 1745. But, he did not have any detailed notes or records of his invention. So, he was given the credit for evolution of the capacitor. A few months later a Dutch professor called Pieter van Musschenbroek found a similar device called the Leyden Jar. Scientists approved this to be the first capacitor. After years, both the scientists have been given equal credit for the invention of the capacitor.

Years later, Benjamin Franklin experimented with the Leyden Jar, and was able to make a smaller capacitor which was named as Franklin Square after him. Later English chemist Michael Faraday began experimenting on the Leyden Jar, and invented the first commercial capacitor. This capacitor was made from large oil barrels. This was later progressed in such a way that electric power could be delivered to very large distances. Click here to know more on the invention history of capacitor.

Working of a Capacitor

A capacitor consists of two metal plates which are separated by a non-conducting substance or dielectric. Take a look at the figure given below to know about dielectric in a capacitor.Though any non-conducting substance can be used as a dielectric, practically some special materials like porcelain, mylar, teflon, mica, cellulose and so on. A capacitor is defined by the type of dielecric selected. It also defines the application of the capacitor.

According to the size and type of dielectric used, the capacitor can be used for high-voltage as well as low-voltage applications.
For applications in radio tuning circuits air is commonly used as the dielectric. for applications in timer circuits mylar is used as the dielectric. For high voltage applications glass is normally used. For application in X-ray and MRI machines, ceramic is mostly preferred.
The metal plates are separated by a distance “d”, and a dielectric material is placed in-between the plates.
The dielectric constant of the dielectric material =  e0e………………e0 is the dielectric of air.

The dielectric material is the main substance that helps in storing the electrical energy.

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