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__Capacitors!__

__Conceptual Physics Eighth Edition__ defines a capacitor as a "device used to store change in a circuit". Capacitors are found in almost all electronic circuits. They are used in laptop and computer keyboards and camera flashes. Huge amounts of energy can also be stored in banks of capacitors. media type="youtube" key="ZYH9dGl4gUE" height="340" width="560" The video above shows how a capacitor works and is made. The video below shows a capacitor being discharged. media type="custom" key="3871851" The picture above shows a capacitor for a typical flash found in a point-and-shoot camera. Capacitors have many uses from calculators to laptops to cameras. NASA also uses glass capacitors to help wake up the space shuttle's circuitry and help deploy space probes. The glass capacitors are typically used for high voltage circuitry, where as a Mylar capacitor is typically used for timer applications like an alarm clock.

Howstuffworks explains a capacitor in a different way. "One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way and can then release them later."

[|This video] shows how hybrid cars are incorporating ultra capacitors into their systems to prolong battery life. "The reason capacitors have fallen out of use is that they require a large surface area to power a device such as a laptop. The MIT researchers have gotten around this by applying nanotechnology to the capacitor. Nanotechnology uses incredibly small materials -- the MIT scientists are using nanotubes, which are 30,000 times thinner than a human hair [source: __[|Science Central]__]. By expanding the amount of matter within the capacitor surface on a nanoscale, the researchers were able to give the capacitor the power required by mobile devices and ectric cars, while reducing the surface area needed to generate the electricity. MIT isn't the only institution taking another look at the capacitor. A team at LG Chemicals has created a hybrid of rechargeable battery and capacitor that is lightweight and biodegradable. The battery can store energy, and the capacitor releases that energy safely in large, predictable amounts. But the plastic battery is still under research, and in its current form won't make it to the market -- it can only hold about the same charge as a traditional alkaline battery, like the ones that power your point-and-shoot digital camera." (Howstuffworks)

Above: An exploding camera flash capacitor.

There are a few ways to increase the amount of charge a capacitor can store. One way is to apply a larger voltage to the capacitor. Another is to decrease the distance between the two conducting plates, also if you increasing the size of the plates it makes it easier to store more charge.

To maximize all space, capacitors are rolled like shown in the picture below. This is why typical capacitors are round.

** What is a capacitor? ** A capacitor  is  a  tool consisting of two conductive plates, each of which has an opposite charge. These plates are separated by an  insulator, which helps them maintain an electric charge. Examples of insulators include ceramic, polyester, tantalum air and polystyrene. Capacitors can be used in digital data which stores analogue signals. Also, capacitors can be used in telecommunications equipment industry. A capacitor can store electrons but cannot make electrons. media type="youtube" key="wBuXeanEFhY" height="344" width="425" This is a video of differnt types of capacitors. The first capacitor  was invented in the 18th century at the Netherlands University. It was called the Leyden jar. The capacitor  consists of  a  glass jar coated with metal on the inside and outside. A rod is connected to the inner coat of metal, passed through the lid of the  capacitor , and has a metal ball on the top of it. Like all capacitors, the Leyden jar contains an oppositely charged electrode and a  plate that is separated by an insulator. The Leyden jar has been used to conduct experiments in electricity for hundreds of years. 
 * History of capacitors**


 * Electrolytic capacitors are polarised. (Shown below)**
 * Polarised capacitors must be connected the correct way round. One of their ends will be marked either positive (+) or negative (-). They are not damaged by heat when soldering.**

Circuit symbol:

Unpolarised Capacitors (shown below) Small value capacitors are unpolarised and may be connected either way round. They are not damaged by heat when soldering, except for polystyrene.

Circuit symbol:



This is a video demonstrates how a capacitor works.

media type="youtube" key="riZkGSXZ7JE" height="344" width="425"

**Parallel Plate Capacitors** Pumped electrons onto the negative plate, electrons are repelled from the negative plate. P ositive charges do not move so a positive charge is induced. The higher the potential difference, the more charge that is crowded onto the negative plate. Also the more electrons that repel from the positive plate creat a charged that is stored.

media type="youtube" key="JyKIenmfUHI" height="344" width="425"This video explains the parts of parallel plate capacitor.

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Electrolytic and Tantalum capacitors are alike in that they are both polarized, meaning that they have a negative and positive side. The difference is that electrolytic capacitors are made up of aluminum and tantalum capacitors are made of tantalum for the electrodes. Also, the tantalum capacitor is able to handle heat and frequency better. Tantalum capacitors are used for circuits that require stability while the electrolytic capacitor is used as a ripple filter in circuits, and are used for low frequency jobs.

electrolytic and tantalum capacitors (piclist.com)

Capacitors are made up of two conductive plates. These plates connect to some sort of power such as a battery. Positive and negative charges build up on either plates (one stores positive charges, the other negative). When the plates are connected, electrons transfer from one plate to the other as the positive battery terminal pulls electrons from the plate connected to it. The electrons pump through the battery into the negative terminal and eventually into the negative plate. The process is complete once the potential difference between the plates equals the potential difference between the battery terminals. They also filter passing charges or currents. They filter the AC (alternating charge) and block the DC (direct charge). Break down voltage is the limited number of voltage that can be used in capacitors. When the voltage exceeds this limit, the dielectric becomes a conductor. The break down voltage is something that needs to be watched and regulated often. It is especially low in electrolytic capacitors. This is displayed as the Working Voltage.