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| '''Electrical resistance''' is the ratio of the ] (i.e. voltage) across an electric component (such as a ]) to the ] passing through it: | |||
| :<math>R=V/I</math> | |||
| (where V is the voltage and I the current) | |||
| It is thus a measure of the component's opposition to the flow of ]. Electrical resistance is usually denoted by symbol ''R''. The ] unit for electrical resistance is ]. Its ] quantity is '''electrical conductance''' measured in ]. | |||
| For a wide variety of materials and conditions, the electrical resistance does not depend on the amount of current flowing or the amount of applied ]: the two are ] and the proportionality constant is the electrical resistance. This is the content of ]. | |||
| Specific electrical resistance, a measure of a material's ability to oppose the flow of electric current, is also known as ]. | |||
| The resistance ''R'' of a wire can be computed as | |||
| :<math> R = {L \rho \over A} \; , </math> | |||
| where ''L'' is the length of the wire, ''A'' is the cross-sectional area and ρ is the electrical resistivity of the material. | |||
| See ] for the more information about the physical mechanisms for conduction in materials. | |||
| Some materials exhibit the property known as ]. | |||
| ==See also== | |||
| *] | |||
| *] | |||