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Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm , while electrical conductance is measured in siemens (S) (formerly called the 'mho' and then represented by ℧). The resistance of an object depends in large part on the material it is made of.
Resistivity is commonly represented by the Greek letter ρ . The SI unit of electrical resistivity is the ohm - metre (Ω⋅m). [ 1 ] [ 2 ] [ 3 ] For example, if a 1 m 3 solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω , then the resistivity of the material is 1 Ω⋅m .
Thermal resistance R: Measure for the ease with which an object resists conduction of heat K/W L −2 M −1 T 3 Θ: extensive Thermal resistivity R λ: Measure for the ease with which a material resists conduction of heat K⋅m/W L −1 M −1 T 3 Θ: intensive Viscosity: η: The measure of the internal friction in a fluid Pa⋅s L −1 M T ...
That means that the contact resistance of the probes and their leads is inseparable from the resistance of the contact area to be measured, with which they are in series. In a four-terminal measurement, the current used to make the measurement is injected using a second, separate pair of leads, so the contact resistance of the measurement ...
Various resistor types of different shapes and sizes. A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.
One of the functions of many types of multimeters is the measurement of resistance in ohms.. The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of one volt (V), applied to these points, produces in the conductor a current of one ampere (A), the conductor not being the seat of any electromotive force.
The electrical conductivity of a solution of an electrolyte is measured by determining the resistance of the solution between two flat or cylindrical electrodes separated by a fixed distance. [4] An alternating voltage is generally used in order to minimize water electrolysis. [citation needed] The resistance is measured by a conductivity meter.
Ohm's law, in the form above, is an extremely useful equation in the field of electrical/electronic engineering because it describes how voltage, current and resistance are interrelated on a "macroscopic" level, that is, commonly, as circuit elements in an electrical circuit.