Essential Information & explanations, latest texts & monographs on
Electrical_resistance.
Electrical resistance
Electromagnetism
Electricity
Electric charge
Coulomb's law
Electromagnetic field
Gauss's law
Electric potential
Electric current
Resistance
Electromotive force
Magnetism
Magnetic field
Ampere's law
Induction
Faraday's law
Maxwell's equations
Electrical resistance is the ratio of the potential difference (i.e. voltage) across an electric component (such as a resistor) to the current passing through it:
where R is the resistance, V the voltage and I the current.
Resistance is thus a measure of the component's opposition to the flow of electric charge. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens. Resistance is constant only for ohmic devices.
Differential resistance or incremental resistance is defined as the slope of the V-I graph at a particular point, thus:
This quantity is sometimes called simply resistance, although the two definitions are equivalent only for an ohmic component such as an ideal resistor. If the V-I graph is not monotonic (i.e. it has a peak or a trough), the differential resistance will be negative for some values of voltage and current. This property is often known as negative resistance, although it is more correctly called negative differential resistance, since the absolute resistance V/I is still positive.
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 case is described by 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
where L is the length of the wire, A is the cross-sectional area and ρ is the electrical resistivity of the material.
See electrical conduction for the more information about the physical mechanisms for conduction in materials.
See also
The above article is adapted from from Wikipedia All Wikipedia article text is available under the terms of the GNU Free Documentation License
Updates and comments at Essential Facts blog
World Class Photographers
Some philosophical movements
|
|
Interesting Links
Latest Dowloadable
Electrical_resistance PDF s & Ebooks
Top PDF and eBook Downloads
Bibliographic Resources
Dates
20-th Century
20-th Century Details
Chromosomes and Genomics
Sports
Kitchen Knowledge
Hollywood Icons
Classical Music
Music Directory.
Music: Jazz
Music: Rock
Music: Country
Music: Popular A-E
Music: Popular F-L
Music: Popular M-S
Music: Popular T-Z
Mythology
Philosophy
Politics
Retirement
Agriculture
Agriculture: Flowers
Agriculture: Gardening
Biology
Biology & Biologists
Cell Science
Cell Science: Cells
Cell Science: Stem Cells
California
Cats & Dogs
Ethics
Electronics
Logic
The Greats
Architectural Dates & Places
Styles ABC
Styles DTOI
Styles JTON
Styles OTOZ
Buddhism
Marketing
Psychology
Enginering Systems 1
Mathematics
Classic Authors
Fear No Exams
Characters & countries
Law & Legal Topics
Linguistics
Movies
Most successful Movies
Science Plus
Science & Computers
Quantum Theory
|