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How Capacitors Work :

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How Capacitors Work :

  • 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.
  • Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting substance, ordielectric. You can easily make a capacitor from two pieces of aluminum foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work.
  • In theory, the dielectric can be any non-conductive substance. However, for practical applications, specific materials are used that best suit the capacitor's function. Mica, ceramic, cellulose, porcelain, Mylar, Teflon and even air are some of the non-conductive materials used. The dielectric dictates what kind of capacitor it is and for what it is best suited. Depending on the size and type of dielectric, some capacitors are better for high frequency uses, while some are better for high voltage applications. Capacitors can be manufactured to serve any purpose, from the smallest plastic capacitor in your calculator, to an Ultracapacitor that can power a commuter bus. NASA uses glass capacitors to help wake up the space shuttle's circuitry and help deploy space probes. Here are some of the various types of capacitors and how they are used.

Air - Often used in radio tuning circuits

Mylar - Most commonly used for timer circuits like clocks, alarms and counters

Glass - Good for high voltage applications

Ceramic - Used for high frequency purposes like antennas, X-ray and MRI machines

Super capacitor - Powers electric and hybrid cars

Capacitor Circuit :

  • In an electronic circuit, a capacitor is shown like this:
  • When you connect a capacitor to a  battery, here's what happens:
  • The plate on the capacitor that attaches to the negative terminal of the battery accepts electrons that the battery is producing.
  • The plate on the capacitor that attaches to the positive terminal of the battery loses electrons to the battery.
  • Once it's charged, the capacitor has the same voltage as the battery (1.5 volts on the battery means 1.5 volts on the capacitor). For a small capacitor, the capacity is small. But large capacitors can hold quite a bit of charge. You can find capacitors as big as soda cans that hold enough charge to light a flashlight bulb for a minute or more.
  • Even nature shows the capacitor at work in the form of lightning. One plate is the cloud, the other plate is the ground and the lightning is the charge releasing between these two "plates." Obviously, in a capacitor that large, you can hold a huge amount of charge!


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