Electrical resistivity and conductivity conductivity in a solution. A rough summary is as follows: This table shows the resistivity (ρ), conductivity and temperature coefficient of various materials at 20 °C (68 °F, 293 K) The effective temperature coefficient varies with temperature and purity level of the material. The 20 °C value is only an approximation when used at other temperatures. For example, the coefficient becomes lower at higher temperatures for copper, and the value 0.00427 is commonly specified at . The extremely low resistivity (high conductivity) of silver is characteristic of metals. George Gamow tidily summed up the nature of the metals' dealings with
Thermal conductivity and it is measured in watts per square metre of surface area for a temperature gradient of 1 K per unit thickness of 1 m". Therefore, specific thermal conductivity is calculated as: where: formula_14 = temperature difference (K, or °C) = 1 K during measurement Absolute thermal conductivity, on the other hand, has units of formula_15 or formula_16, and can be expressed as where formula_18 = absolute thermal conductivity (W/K, or W/°C). Substituting formula_18 for formula_20 into the first equation yields the equation which converts from absolute thermal conductivity to specific thermal conductivity: Solving for formula_18, we get the equation