Saturday, January 16, 2010

Farad

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the unit in which CAPACITANCE is measured. It is usually denoted by the symbol F. For example, the capacitance (C) of a conductor measured in farads is the charge (in coulombs) needed to raise the potential by one volt i.e. 1 farad = 1 coulomb per volt (1F = 1 CV-1). As the farad itself is usually too large a quantity for most applications, the practical unit is the microfarad (µF), or one millionth of a farad.

Taken from Dictionary of Science

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The farad (symbol: F) is the SI unit of capacitance. The term farad is named after the English physicist Michael Faraday.

A farad is the charge in coulombs a capacitor will accept for the potential across it to change 1 volt. A coulomb is 1 ampere second. Example: A 47 mA current causes the voltage across a capacitor to increase 1 volt per second. It therefore has a capacitance of 47 mF. It has the base SI representation of s4·A2·m-2·kg-1. Further equalities follow:


\mbox{F} = \,\mathrm \frac{A \cdot s}{V} = \dfrac{\mbox{J}}{\mbox{V}^2} = \dfrac{\mbox{C}}{\mbox{V}} = \dfrac{\mbox{C}^2}{\mbox{J}} = \dfrac{\mbox{C}^2}{\mbox{N} \cdot \mbox{m}} = \dfrac{\mbox{s}^2 \cdot \mbox{C}^2}{\mbox{m}^{2} \cdot \mbox{kg}} = \dfrac{\mbox{s}^4 \cdot \mbox{A}^2}{\mbox{m}^{2} \cdot \mbox{kg}} = \dfrac{\mbox{s}}{\Omega}


The most commonly used multiples and submultiples in electrical and electronic usage are the microfarad, nanofarad and picofarad.


Taken from Wikipedia



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