There are two types of charge carriers in substances: electrons or ions. The movement of these charges creates an electric current.

All metals are characterized by electronic conductivity. Violation of the crystal lattice impedes the movement of electrons (for example, when an impurity is added) and thereby increases the resistivity.

Liquids are characterized by ionic conductivity. Distilled water practically does not conduct current. But if you add a soluble salt to the water, which dissociates into ions, then the more salt and the greater part of it decomposes into ions, the higher the conductivity of the solution. This is the first factor affecting the conductivity (ion concentration) ...

Temperature regulators - what is it? The name itself already shows that this is a device, a mechanism by which you can adjust the temperature.

In everyday life, temperature controllers are found in almost all devices where one way or another it is necessary to regulate or maintain the temperature within specified limits. In this article we will try to figure out where, how and which temperature controllers are used.

The most common are three types of temperature controllers: electronic, electromechanical, mechanical. All three types of temperature regulators, one way or another intersect each other, in terms of design. Let's consider each type of temperature regulators in more detail ...

The power electrical equipment of the house includes pumps, fans, compressors, mechanisms for opening gates and other mechanisms equipped with electric motors.

If the house is powered by a three-phase circuit, then it is advisable to use three-phase power (and thermal) equipment. To drive such mechanisms with three-phase power, an asynchronous three-phase motor is most often used.

Information about the engine is indicated in its passport (in the documentation and on a metal plate attached to the body). Nominal values ​​are given here, i.e. those for which the engine is designed during its normal operation at the maximum permissible load ...

What nation would not like to call one of its sons the inventor of radio and to rank the priority of the great discovery behind their homeland? That is why disputes among the historians of science have not ceased for a century.

The most convincing arguments and opinions are presented, in which there are not so many names: Maxwell (England), Hertz (Germany), Branly (France), Popov (Russia), Marconi (Italy).

But even among them, an American engineer Lee de Forest It seems that the figure, at first glance, is not quite suitable for the role of the founder of the radio. But why, in the homeland of a scientist engineer, in the USA, is his name pronounced in combination with the words “father of radio” and even “grandfather of television”? Indeed, there must be good reason for this. And they are ...

The article talks about the design of LED lamps. Several schemes of different complexity are considered and recommendations are given for the independent manufacture of LED light sources connected to a 220 V network.

As a result of the global crisis, the problem of energy conservation has become even more urgent throughout the world. In this regard, from September 1, 2009, in 27 countries of the European Union, the sale of incandescent lamps with a capacity of 100 or more watts has already been banned. And already in 2011 in Europe, it is planned to introduce an embargo on the sale of the most popular 60-watt light bulbs for buyers. By the end of 2012, a complete rejection of incandescent lamps is planned.

The U.S. Congress passed a law on the rejection of incandescent lamps in 2013.According to these laws, residents of the European Union and the United States will fully switch to energy-saving light sources - fluorescent and LED lamps ...

The school physics course describes how the resistance of conductors changes when heated - it increases.

The coefficient of relative increase in resistivity during heating for most metals is close to 1/273 = 0.0036 1 / ° С (differences are in the range of 0.0030 - 0.0044). And how does the resistance of a metal change during its melting?

Figure 1 shows a graph of the change in the resistivity of copper during heating. As can be seen, at a melting temperature, a jump in resistance of 2.07 times is observed.

Thus, from the normal temperature (20 ° С) to the melting temperature, the specific resistance of copper increases by 5.3 times (coefficient K1), while melting it increases by 2.07 times (coefficient K2), and only 10.82 times. ..

For the correct choice of wire cross-section, it is necessary to take into account the value of the maximum current consumed by the load. The current value is easy to determine, knowing the nameplate power of consumers according to the formula I= R / 220 (for example, for an electric heater with a power of 2000 W, the current will be 9 A, for 60 W of a bulb - 0.3 A).

Knowing the total current of all consumers and taking into account the ratio of the allowable current load for the wire of the open load on the wire cross section (for copper wire 10 A per 1 mm, for aluminum wire 8 A per 1 mm), you can choose a wire.

When performing hidden wiring (in a tube or in a wall), the values ​​given must be multiplied by a correction factor of 0.8. It should be noted that open wiring is usually performed with a wire of at least 4 mm cross section² based on sufficient mechanical strength ...

Electronic devices with two stable output states are called triggers. A trigger is translated into one of the stable states by input pulses.

A similar formulation is given, as a rule, in all technical literature. For the one who came across it for the first time, it may not be entirely clear. What are these two states, and why are they called stable?

The easiest way to explain this is with a simple and accessible example. A fairly close and understandable analogue can be an ordinary light bulb with a switch. There are two states here: on - off. For a trigger, these states are high, low. It is also sometimes said, on - off, installed - reset.

In order to light or turn off the light bulb, just touch the switch. In order for the bulb to continue to burn, it is not necessary to hold the switch with your finger: the bulb will burn indefinitely ...