Search results
Results From The WOW.Com Content Network
Resistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current .
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 ...
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.
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 ...
Specific electrical resistance (also known as electric resistivity) Specific airway resistance (R aw /functional residual capacity (FRC) Cost of transport - specific resistance due to friction for a mechanism transporting mass
In practice, the internal resistance of a battery is dependent on its size, state of charge, chemical properties, age, temperature, and the discharge current. 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 ...
is the thermal resistivity (K·m/W) of the sample; is the cross-sectional area (m 2) perpendicular to the path of heat flow. In terms of the temperature gradient across the sample and heat flux through the sample, the relationship is:
In practical devices, the linear approximation model (above) is accurate only over a limited temperature range. Over wider temperature ranges, a more complex resistance–temperature transfer function provides a more faithful characterization of the performance. The Steinhart–Hart equation is a widely used third-order approximation: