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Some materials lose all electrical resistivity at sufficiently low temperatures, due to an effect known as superconductivity. An investigation of the low-temperature resistivity of metals was the motivation to Heike Kamerlingh Onnes's experiments that led in 1911 to discovery of superconductivity. For details see History of superconductivity.
Resistivity and conductivity are reciprocals: = /. Resistivity is a measure of the material's ability to oppose electric current. This formula is not exact, as it assumes the current density is totally uniform in the conductor, which is not always true in practical situations. However, this formula still provides a good approximation for long ...
In schematic diagrams, a resistor is shown as a long rectangle or zig-zag symbol. An element (resistor or conductor) that behaves according to Ohm's law over some operating range is referred to as an ohmic device (or an ohmic resistor ) because Ohm's law and a single value for the resistance suffice to describe the behavior of the device over ...
Skin effect itself is not actually combatted in these cases, but the distribution of currents near the conductor's surface makes the use of precious metals (having a lower resistivity) practical. Although it has a lower conductivity than copper and silver, gold plating is also used, because unlike copper and silver, it does not corrode.
The tunnel diode circuit (see diagram) is an example. [82] The tunnel diode TD has voltage controlled negative differential resistance. [ 54 ] The battery V b {\displaystyle V_{b}} adds a constant voltage (bias) across the diode so it operates in its negative resistance range, and provides power to amplify the signal.
The current–voltage characteristics of four devices: a resistor with large resistance, a resistor with small resistance, a P–N junction diode, and a battery with nonzero internal resistance.
Sheet resistance is a special case of resistivity for a uniform sheet thickness. Commonly, resistivity (also known as bulk resistivity, specific electrical resistivity, or volume resistivity) is in units of Ω·m, which is more completely stated in units of Ω·m 2 /m (Ω·area/length). When divided by the sheet thickness (m), the units are Ω ...
It has an electronic component due to the resistivity of the component materials and an ionic component due to electrochemical factors such as electrolyte conductivity, ion mobility, speed of electrochemical reaction and electrode surface area. Measurement of the internal resistance of a battery is a guide to its condition, but may not apply at ...