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'''[[Capacitance]]''' is a measure of the amount of [[electric charge]] stored (or separated) for a given [[electric potential]]. The capacitance of the majority of capacitors used in electronic circuits is several orders of magnitude smaller than the farad. The [[energy]] (measured in [[joule]]s) stored in a capacitor is equal to the ''work'' done to charge it. | |||
:<math>C = \frac{Q}{V}</math> | |||
In a [[capacitor]], there are two conducting electrodes which are insulated from one another. The charge on the electrodes is +Q and -Q, and V represents the potential difference between the electrodes. The [[SI]] unit of capacitance is the [[farad]]; 1 farad = 1 [[coulomb]] per [[volt]]. | |||
:<math>C = \epsilon \frac{A}{d}</math> | |||
The capacitance can be calculated if the geometry of the conductors and the dielectric properties of the insulator between the conductors are known, such as above, where; ''C'' is the capacitance in [[farads]], ''ε'' is the [[permittivity]] of the insulator used (or [[physical constants|''ε''<sub>0</sub>]] for a vacuum), ''A'' is the area of each plane electrode in square metres, ''d'' is the separation between the electrodes in metres. The equation is a good approximation if ''d'' is small compared to the other dimensions of the electrodes. | |||
Revision as of 05:50, 5 September 2012
Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. The capacitance of the majority of capacitors used in electronic circuits is several orders of magnitude smaller than the farad. The energy (measured in joules) stored in a capacitor is equal to the work done to charge it.
In a capacitor, there are two conducting electrodes which are insulated from one another. The charge on the electrodes is +Q and -Q, and V represents the potential difference between the electrodes. The SI unit of capacitance is the farad; 1 farad = 1 coulomb per volt.
The capacitance can be calculated if the geometry of the conductors and the dielectric properties of the insulator between the conductors are known, such as above, where; C is the capacitance in farads, ε is the permittivity of the insulator used (or ε0 for a vacuum), A is the area of each plane electrode in square metres, d is the separation between the electrodes in metres. The equation is a good approximation if d is small compared to the other dimensions of the electrodes.