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CAPACITOR : DEFINITION AND HISTORY



For all practical purposes, consider only the parallel-plate capacitor: two conductors or electrodes separated by a dielectric material of uniform thickness.  The conductors can be any material which will conduct electricity easily. The dielectric material must be a poor conductor – an insulator.

In October 1745, Ewald Georg von Kleist of Pomerania in Germany found that charge could be stored by connecting a generator by a wire to a volume of water in a hand-held glass jar. Von Kleist's hand and the water acted as conductors and the jar as a dielectric. Von Kleist found that after removing the generator, touching the wire resulted in a spark. In a letter describing the experiment, he said "I would not take a second shock for the kingdom of France." The following year, the Dutch physicist Pieter van Musschenbroek invented a similar capacitor, which was named the Leyden jar, after the University of Leyden where he worked. Daniel Gralath was the first to combine several jars in parallel into a "battery" to increase the charge storage capacity.

A capacitor is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When there is a potential difference (voltage) across the conductors, a static electric field develops across the dielectric, causing positive charge to collect on one plate and negative charge on the other plate. Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them.

In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons on the other terminal. A capacitor is much simpler than a battery, as it can't produce new electrons -- it only stores them. In this article, we'll learn exactly what a capacitor is, what it does and how it's used in electronics. We'll also look at the history of the capacitor and how several people helped shape its progress.

There are a variety of other capacitors including: Ceramic capacitors that are suitable for use in high frequency applications. They have a low capacitance, but are stable at high frequency. They can also work in hot environments.Tantalum bead capacitors, which use an electrolytic principle.  They are very small in size, but can have values of up to 10 microF.

An electrolytic capacitor is a type of capacitor that uses an electrolyte, an ionic conducting liquid, as one of its plates, to achieve a larger capacitance per unit volume than other types. They are often referred to in electronics usage simply as "electrolytics". They are used in relatively high-current and low-frequency electrical circuits, particularly in power supply filters, where they store charge needed to moderate output voltage and current fluctuations in rectifier output. They are also widely used as coupling capacitors in circuits where AC should be conducted but DC should not. There are two types of electrolytics; aluminum and tantalum.

1745 - The history of the capacitor varies, though records indicate a German invented the capacitor in 1745. Read more about the history of the capacitor.From Capacitor : History - Related web pages

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