Driving in any conductor, electric currenttransmits some energy to it, which is why the conductor heats up. Energy transfer occurs at the level of molecules: as a result of the interaction of the electrons of the current with the ions or atoms of the conductor, some of the energy remains with the latter.
The thermal effect of the current leads to faster movement of the conductor particles. Then its internal energy increases and is transformed into heat.
Тепловое действие тока может быть подтверждено different experiences, where the work of the current goes to the internal conductor energy. In this case, the latter increases. Then the conductor gives it to the surrounding bodies, that is, heat transfer occurs with the conductor heating.
The formula for the calculation in this case is as follows: A = U * I * t.
The amount of heat can be denoted by Q. Then Q = A or Q = U * I * t. Knowing that U = IR, it turns out Q = I * R * t, which was formulated in the Joule-Lenz law.
Conductor where the electric current flows,studied by many scientists. However, the most notable results were achieved by James Joel from England and Emilia Christian Lenz from Russia. Both scientists worked separately and the conclusions on the results of the experiments were made independently of one another.
They deduced the law, allowing to estimate the heat received as a result of action of current on the conductor. He was called the law of Joule-Lenz.
Consider in practice the thermal effect of current. Examples are the following:
The thermal effect of the current and the discovery of the lawcontributed to the development of electrical engineering and increased opportunities for the use of electricity. The way research results are applied can be seen on the example of an ordinary incandescent bulb.
It is designed in such a way that insideA thread made of tungsten wire is pulled. This metal is refractory with high resistivity. When passing through the bulb, the thermal effect of electric current is carried out.
Conductor energy is transformed into heat,the spiral heats up and starts to glow. The lack of light bulbs is a large energy loss, since it is only due to a small part of the energy that it starts to glow. The main part just heats up.
Чтобы лучше это понять, вводится коэффициент efficacy that demonstrates performance and conversion to electricity. Efficiency and thermal effect of current are used in different areas, since there are many devices made on the basis of this principle. To a large extent these are heating appliances, electric stoves, boilers and other similar devices.
Usually in the design of all appliances for heatingThere is a metal spiral, the function of which includes heating. If water is heated, the helix is installed in isolation, and in such devices a balance between energy from the network and heat exchange is provided.
Scientists are constantly tasked toreducing energy losses and finding the best ways and the most effective schemes for their implementation in order to reduce the thermal effect of the current. For example, a method of increasing the voltage during the transmission of energy is used, thereby reducing the current intensity. But this method, at the same time, reduces the safety of the operation of power lines.
Another research area isselection of wires. After all, heat loss and other indicators depend on their properties. In addition, during the operation of heating devices, a large release of energy occurs. Therefore, the spirals are made of specially designed for this purpose, capable of withstanding high loads, materials.
To improve protection and secure electricalcircuits, special fuses are used. In the role of the main part serves wire of low-melting metal. It takes place in a cork of porcelain, has a screw thread and a contact in the center. The plug is inserted into the cartridge located in the porcelain box.
Lead wire is part of a common chain.If the thermal effect of the electric current increases dramatically, the conductor cross section will not stand, and it will begin to melt. As a result of this, the network will open, and current overloads will not occur.
Electric arc is a fairly efficient converter of electrical energy. It is used in the welding of metal structures, and also serves as a powerful light source.
The basis of the device includes the following.Take two carbon rods, connect the wires and attach them to the insulating holders. After that, the rods are connected to a current source, which gives a small voltage, but is designed for a large amperage. Connect the rheostat. Coals should not be included in the city network, as this may cause a fire. If you touch one coal on another, you can see how much they will glow. It is better not to look at this flame, because it is harmful to the eyes. An electric arc is used in furnaces for smelting metal, as well as in such powerful lighting devices as spotlights, film projectors, etc.
