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Because both the thermal and electrical conductivity correlate with the charge carriers, new means must be introduced in order to conciliate the contradiction between high electrical conductivity and low thermal conductivity, as is needed. [23] When selecting materials for thermoelectric generation, a number of other factors need to be considered.
A 2008 review paper written by Philips researcher Clemens J. M. Lasance notes that: "Although there is an analogy between heat flow by conduction (Fourier's law) and the flow of an electric current (Ohm’s law), the corresponding physical properties of thermal conductivity and electrical conductivity conspire to make the behavior of heat flow ...
In alloys the change in electrical conductivity is usually smaller and thus thermal conductivity increases with temperature, often proportionally to temperature. Many pure metals have a peak thermal conductivity between 2 K and 10 K. On the other hand, heat conductivity in nonmetals is mainly due to lattice vibrations . Except for high-quality ...
Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact. The higher temperature object has molecules with more kinetic energy ; collisions between molecules distributes this kinetic energy until an object has the same kinetic energy throughout.
Electrical energy is linearly translated to thermal energy as electrical conductivity increases, and this is the key process parameter that affects heating uniformity and heating rate. [11] This heating method is best for foods that contain particulates suspended in a weak salt containing medium due to their high resistance properties. [10]
The ratio between the emf and temperature difference is the Seebeck coefficient. A thermocouple measures the difference in potential across a hot and cold end for two dissimilar materials. This potential difference is proportional to the temperature difference between the hot and cold ends.
The thermal conductivity κ in crystalline solids has mainly two components: κ = κ electron + κ phonon. According to the Wiedemann–Franz law, the higher the electrical conductivity, the higher κ electron becomes. [13] Thus in metals the ratio of thermal to electrical conductivity is about fixed, as the electron part dominates.
The electrons are bumped to the conduction energy band by thermal energy, where they flow freely, and in doing so leave behind holes in the valence band, which also flow freely. The electric resistance of a typical intrinsic (non doped) semiconductor decreases exponentially with temperature following an Arrhenius model: