Dissipation, of electrical energy

It is instructive to consider important features of the design of high-power capacitors in some detail, particularly with regard to power dissipation. The average rate P at which heat is developed in a dielectric due to the dissipation of electrical energy is... 

Resistance heating n. Heating by means of dissipation of electrical energy in resistive circuit elements. The rate of heating (W) is given by the quotient of the square of the voltage drop across the heater (V ) divided by its at-temperature resistance (fi), also by the product of the voltage drop and the current (VA). 

These three effects are potentially reversible processes, in contradistinction with the Joule effect (dissipation of electric energy into heat) and with heat transfer (Eourier equation) that are irreversible processes. Nevertheless, all these processes may coexist in the same material or system. When the coupling factor is a constant, it takes the name of Seebeck coefficient, and only the Peltier and Seebeck effects are observed. 

Here, kr is the CCL thermal conductivity and Rreac is the volumetric rate of electrochemical conversion (A cm ). Equation 4.282 says that the variation of conductive heat flux (the left-hand side) equals the sum of the heating rates from the reaction and the Joule dissipation of electric energy. On the other hand, determines the rate of proton current decay along x ... 

Electrical resistance leads to dissipation of electrical energy in the form of Joule heating. Similarly, hydraulic resistance leads to viscous dissipation of mechanical energy into heat by internal friction in the fluid. The role of viscous dissipation can be explained based on the schematic of transient flow behavior shown in Figure 2.9. Let an incompressible Poiseuille fluid flow takes place inside a channel at times t < 0. The constant Poiseuille-type velocity field is maintained by a constant over-pressure AP applied to the left end of the channel. The over-pressure AP is suddenly removed at time, t = 0. However, the fluid flow continues due to the inertia of the fluid. The internal viscous friction of the fluid gradually slows down the motion of the fluid, and eventually in the limit t - c the fluid comes to rest relative to the channel walls. As time passes, the kinetic energy of the fluid at t = 0 is gradually transformed into heat by the viscous friction. 

The heat capacity must be determined if it is not known. A direct method, which depends on the assumption of the constancy of heat capacities over a small range of temperature, is to measure the adiabatic temperature rise (/) — 7j) produced by the dissipation of a measured quantity of electrical energy. We then obtain... 

Fillers may decrease thermal conductivity. The best insulation properties of composites are obtained with hollow spherical particles as a filler. Conversely, metal powders and other thermally conductive materials substantially increase the dissipation of thermal energy. Volume resistivity, static dissipation and other electrical properties can be influenced by the choice of filler. Conductive fillers in powder or fiber form, metal coated plastics and metal coated ceramics will increase the conductivity. Many fillers increase the electric resistivity. These are used in electric cable insulations. Ionic conductivity can be modified by silica fillers. 

Successful AF ablation depends upon achieving lesions that are reliably transmural (135,136). Radiofrequency energy consists of alternating electrical current which can be delivered to the myocardial tissue through a transvenous electrode catheter. The tissue resistivity results in dissipation of RF energy as heat, which conducts passively to deeper tissue layers. Most tissues exposed to temperatures of 50°C or higher for more than several seconds will show irreversible coagulation necrosis and... 

When using QCM sensors in liquid media one faces a considerably more involved situation. The behavior of QCRs under these conditions diverges essentially from that in vacuum or gaseous media. Most important is the significant dissipation of acoustic energy due to liquid contact, which translates to energy lost from the electrical circuit. The oscillation is significantly... 

Ratio of the conductance of a capacitor in which the material is dielectric to its substance, or the ratio of its parallel reactivity to its parallel resistance. Most plastics have a low dissipation factor, a desirable property because it minimizes the waste of electrical energy as heat. 

Dissipation di-s9- pa-shon n. The loss modulus in a plastic part when imparted with rapid, cyclic changes (or even reversals) of stress. The product of mechanical dissipation is heat, which can raise the temperature of the part and cause it to weaken, creep rapidly, or even fail prematurely. Dissipation can also apply to electrical systems, whereby a material with small dissipation will tend to better insulate heat. This is a desirable property in electrical insulations for high-frequency applications because it minimizes the waste of electrical energy as heat. 

The Seebeck effect corresponds to the electricity production from a difference of temperature. This effect can be reversible and is the inverse of the Peltier effect, which is the phenomenon of conversion of electric energy into thermal energy (heat). These effects can be superimposed onto the dissipative processes of transport by conduction of electric charges (Joule effect) and to the transport of heat (Fourier equation) which are both irreversible processes. 

The Peltier effect is a conversion of electrical energy into heat that has the remarkable property to be potentially reversible, unlike the Joule effect that also converts into heat, but by completely irreversible degradation (dissipation). The reverse process of the Peltier effect is the Seebeck effect. 

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