Scientists have created new superconducting compounds of hydrogen and praseodymium, a rare-earth metal, one substance being quite a surprise from the perspective of classical chemistry. The study helped find the optimal metals ...
Superconductivity
Mar 03, 2020
0
70
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Nanophysics
Feb 19, 2020
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305
Graphene is often seen as the wonder material of the future. Scientists can now grow perfect graphene layers on square centimetre-sized crystals. A research team from the University of Göttingen, together with the Chemnitz ...
Nanomaterials
Jan 29, 2020
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3
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Ecology
Jan 27, 2020
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357
Nanosafety researchers at the Harvard T.H. Chan School of Public Health have developed a new intervention to fight infectious disease by more effectively disinfecting the air around us, our food, our hands, and whatever else ...
Bio & Medicine
Jan 24, 2020
1
10
Nanowalls, nanobridges, nano "jungle gyms": It could seem like the description of a Lilliputian village, but these are actual 3-D-printed components with potential applications in nanoelectronics, smart materials and biomedical ...
Nanomaterials
Dec 19, 2019
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51
For the first time, researchers have been able to record, frame-by-frame, how an electron interacts with certain atomic vibrations in a solid. The technique captures a process that commonly causes electrical resistance in ...
Optics & Photonics
Dec 10, 2019
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3872
Researchers from the Moscow Institute of Physics and Technology, Lomonosov Moscow State University, and the Institute of Solid State Physics of the Russian Academy of Sciences have demonstrated the possibility of detecting ...
Superconductivity
Dec 09, 2019
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125
Superconducting circuits, which have zero electrical resistance, could enable the development of electronic components that are significantly more energy-efficient than most chips used today. Importantly, superconducting ...
Electric shocks are used to heat gluten-free bread from the inside, saving energy and time compared to conventional baking applying heat from the outside. A recent study from the Institute of Food Technology of the University ...
Other
Oct 24, 2019
0
967
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
