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Superconductivity
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In a study published in Nano Letters, researchers have demonstrated a new technique to measure the quantum excitations in superconducting materials with atomic precision for the first time. Detecting these excitations is ...
Superconductivity
Jun 03, 2022
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253
A group of researchers from Pisa, Jyväskylä, San Sebastian and MIT have demonstrated how a heterostructure consisting of superconductors and magnets can be used to create unidirectional current like that found in semiconductor ...
Superconductivity
May 11, 2022
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854
Superconductors are materials that can achieve a state known as superconductivity, in which matter has no electrical resistance and does not allow the penetration of magnetic fields. At low temperatures, these materials are ...
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Cell & Microbiology
May 04, 2022
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112
Rather than digging to identify unmarked mass grave sites or evidence to locate missing persons, cutting-edge technologies are helping law enforcement agents, forensic scientists and historians uncover attempts to hide victims.
Earth Sciences
Apr 12, 2022
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Copper (Cu) is of fundamental importance to our daily lives due to its excellent electrical conductivity, as well as other valuable physical properties, such as the ability to draw copper into thin wires. Cu is the metal ...
Materials Science
Mar 21, 2022
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250
Semiconductors are the foundation of modern technology while superconductors with their zero electrical resistance could become the basis for future technologies, including quantum computers. So-called "hybrid structures"—carefully ...
Superconductivity
Mar 16, 2022
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239
A quasiparticle that forms in semiconductors can now be moved around at room temperature, a University of Michigan-led study has shown. The finding could cool down computers, enabling faster speeds and higher efficiencies, ...
Optics & Photonics
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400
In most Latin American countries where there has been a high level of civil conflict over the past few decades, there are still huge numbers of missing people due to forced disappearances. In Colombia alone this number is ...
Archaeology
Jan 13, 2022
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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
