| Revision as of 19:06, 23 November 2002 edit198.81.26.198 (talk) Resistance in a nut shell← Previous edit | Revision as of 00:32, 25 November 2002 edit undoAxelBoldt (talk | contribs)Administrators44,502 editsNo edit summaryNext edit → | ||
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| '''Electrical resistance''' is the ratio of the ] across an electric component (such as a ]) to the ] passing through it. 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 resistance can be one of two things. It can either be the resistance of a resistor in a a circut, or the resistance of a wire or both. In simple terms, the amount of Voltage you have in a wire is equal to the Current times the resistance. Voltage can be thought of as how swiftly a river is flowing. Current could be thought of how "wide" the river is, or in other words, how much water is flowing through the river at a given time. ex. A small stream would be small current, while the colorado river would be a lot of current. And resistance can be thought of as the river banks. So if resistance is high, there's a lot of narrowing in the river. If resisatance is low, the river runs wide and free. So that is resistance in its relation to "resistors" in an electrical circut. Now wire resistance is a different story. In order to find it you need 3 things. A. If you chop a section of wire, how much cross-sectional area does the wire cover. B. how "long" is the wire. C. The metallic constant which is dependant upon the metal you use, and the temperature of the metal. | |||
| 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 | |||
| :''R'' = ''L''ρ/''A'' | |||
| where ''L'' is the length of the wire, ''A'' is the cross-sectional area and ρ is the electrical resistivity of the material. | |||
Revision as of 00:32, 25 November 2002
Electrical resistance is the ratio of the potential difference across an electric component (such as a resistor) to the current passing through it. It is thus a measure of the component's opposition to the flow of electric charge. Electrical resistance is usually denoted by symbol R. The SI unit for electrical resistance is ohm. Its reciprocal quantity is electric conductance.
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 voltage: the two are proportional and the proportionality constant is the electrical resistance. This is the content of Ohm's law.
Specific electrical resistance, a measure of a material's ability to oppose the flow of electric current, is also known as electrical resistivity.
The resistance R of a wire can be computed as
- R = Lρ/A
where L is the length of the wire, A is the cross-sectional area and ρ is the electrical resistivity of the material.