The reason for heating the conductor lies in the fact thatthe energy of electrons moving in it (in other words, the energy of a current) is converted into a warm type of energy, or Q, by successive collisions of particles with ions of the molecular lattice of a metal element, thus forming the concept of “thermal power”.
Current performance is measured using internationalSI system of units, applying to it joules (J), the power of the current is defined as "watts" (W). Departing from the system in practice, they can also use non-systemic units that measure current performance. Among them, the watt-hour (Wh × h), kilowatt-hour (abbreviated as kW × h). For example, 1 Wh × h indicates current operation with a specific power of 1 watt and a duration of one hour.
If the electrons move on immobilemetal conductor, in this case all the useful work of the generated current is distributed to the heating of the metal structure, and, based on the provisions of the law of conservation of energy, this can be described by the formula Q = A = IUt = I2Rt = (U2/ R) * t.Such relations express the Joule-Lenz law with accuracy. Historically, it was first determined experimentally by the scientist D. Joel in the middle of the 19th century, and at the same time independently by another scientist - E. Lenz. Thermal power has found practical application in the technical performance of the invention in 1873 by the Russian engineer A. Ladygin of an ordinary incandescent lamp.
Thermal power current is used in a number ofelectrical appliances and industrial installations, namely, in heat metering devices, heating type electric stoves, electric welding and inventory equipment, household appliances are very common in the electric heating effect - boilers, soldering irons, kettles, irons.
Finds a thermal effect in foodindustry. With a high share of use, the possibility of electrical heating is applied, which guarantees thermal power. It is caused by the fact that the current and its thermal power, influencing the food product, which has a certain degree of resistance, causes a uniform heating in it. It is possible to cite as an example how sausages are made: through a special metering device, the meat comes in metal forms, the walls of which simultaneously serve as electrodes. It ensures constant uniformity of heating over the entire area and volume of the product, maintains the set temperature, maintains the optimal biological value of the food product, together with these factors, the duration of technological work and energy consumption remain the least.
Specific thermal power of electric current(ω), in other words, the amount of heat that is released in a unit of volume for a certain unit of time is calculated as follows. The elementary cylindrical volume of the conductor (dV), with a cross-sectional conductor cross section dS, length dl parallel to the direction of the current, and resistance make up the equations R = p (dl / dS), dV = dSdl.
According to the definitions of the Joule-Lenz law, for the allotted time (dt) in the volume taken by us, a level of heat equal to dQ = I2Rdt = p (dl / dS) (jdS)2dt = pj2dVdt. In this case, ω = (dQ) / (dVdt) = pj2 and applying here Ohm’s law to establish the current density j = γE and the relation p = 1 / γ, we immediately get the expression ω = jE = γE2. In differential form, it gives an idea of the Joule-Lenz law.
