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General Physics
May 06, 2019
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49
Modern macroeconomics has failed to produce an understanding of economies in times of crisis. Modern macroeconomics are still based on the assumption of equilibria, but a shock pushes economies out of a state of equilibrium. ...
Economics & Business
Apr 16, 2019
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9
Advanced robotics sensitive touch or next-generation wearable devices with sophisticated sensing capabilities could soon be possible following the development of a rubber that combines flexibility with high electrical conductivity.
Materials Science
Apr 12, 2019
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183
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Nanomaterials
Mar 20, 2019
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28
Researchers in China and at UC Davis have measured high conductivity in very thin layers of niobium arsenide, a type of material called a Weyl semimetal. The material has about three times the conductivity of copper at room ...
Condensed Matter
Mar 18, 2019
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85
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Nanophysics
Feb 26, 2019
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388
Water molecules distort the electrical resistance of graphene, but a team of European researchers has discovered that when this two-dimensional material is integrated with the metal of a circuit, contact resistance is not ...
Nanomaterials
Jan 30, 2019
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35
Researchers at the George Washington University have taken a major step toward reaching one of the most sought-after goals in physics: room temperature superconductivity.
Superconductivity
Jan 15, 2019
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13335
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Robotics
Dec 11, 2018
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8
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Engineering
Nov 20, 2018
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7
The electrical resistance of an object is a measure of its opposition to the passage of a steady electric current. An object of uniform cross section will have a resistance proportional to its length and inversely proportional to its cross-sectional area, and proportional to the resistivity of the material.
Discovered by Georg Ohm in the late 1820s, electrical resistance shares some conceptual parallels with the mechanical notion of friction. The SI unit of electrical resistance is the ohm, symbol Ω. Resistance's reciprocal quantity is electrical conductance measured in siemens, symbol S.
The resistance of a resistive object determines the amount of current through the object for a given potential difference across the object, in accordance with Ohm's law:
where
For a wide variety of materials and conditions, the electrical resistance does not depend on the amount of current through or the amount of voltage across the object, meaning that the resistance R is constant for the given temperature. Therefore, the resistance of an object can be defined as the ratio of voltage to current:
In the case of nonlinear objects (not purely resistive, or not obeying Ohm's law), this ratio can change as current or voltage changes; the ratio taken at any particular point, the inverse slope of a chord to an I–V curve, is sometimes referred to as a "chordal resistance" or "static resistance".
This text uses material from Wikipedia, licensed under CC BY-SA
