In cities, cable television has almost completely replaced the “wireless” competitors, but there is still a demand for TV antennas. In order to receive on-air TV you need to choose a device suitable for your area in design and range. Especially often this need arises in the countryside and the private sector. In this article we will consider what are the antennas for the TV and how to choose it correctly.

Before moving on to talking about the types of television antennas, it is worth talking about the basic terms that will be used in the article. Repeater - a device that receives and amplifies a radio signal and transmits to its subscribers. People call it a TV tower. Antenna - a device for receiving or transmitting radio waves. Its main task is to convert electromagnetic waves into signals the other way around. It is connected to the receiver, in our case, to the TV ...

Most of the equipment that runs on electricity is powered by wires. But their veins and insulation are not eternal, so the wires are thrown or torn, or their insulation is frayed. In this article, we will consider the main malfunctions and methods of repairing wires, cables and cords.

In the everyday sense, wires, cables and cords do not have significant design differences. The insulation or flexibility class of the core may be modified, but in both senses there is not much difference. It is worth noting that, when it comes to mobile equipment, for example: iron, electric drill, grinder, charging for the phone - their conductors are called cords. If we are talking about wiring internal or external - such conductors are called cables (not always, depending on the product used), but if we are talking about connections inside devices or extensions, these are most often wires.All cable products consist of ...

LED lighting fixtures and lamps are no longer a novelty for a long time, but often an ordinary person does not understand what he is buying at the store and whether a simple light bulb can somehow affect his health. The fact is that the quality of a light source is not determined by its power and how much light it gives out. These are just quantitative indicators, an indicator of the quality of light is the ripple coefficient and color rendering index.

As already mentioned, the quality of the lamps determines not their brightness, but such indicators as the ripple coefficient and color rendering index. These two characteristics determine both the perception of light and your well-being. You may have noticed that when you spend a lot of time, for example, in a garage with old fluorescent lamps, your head sometimes starts to hurt and there is some feeling of unnatural surroundings, and if you go out into the sun everything seems much more saturated and more pleasant for the eye ...

Replacing the outlet is simple, but not always everything goes as you want. It often happens that you can’t just take and plug in a new outlet, because the length of the old wires is not enough. They can break off or simply the design of the new outlet is different and it is not possible to clamp the wires normally. In this article, we will look at ways to lengthen short wires.

Wires and cables can have single-wire cores - these are cores that consist of a single solid wire, they are called rigid or monolithic cores. Frequent bending may break. Another type - multi-wire veins - they are soft, consist of several thin wires. It is often called stranded or flexible to bend such wires. The number of wires depends on the flexibility class of the core - the higher it is, the more wires.How does this relate to the extension of wires in the outlet? The fact is that the method of connecting them depends on the type of cores ...

Thermocouples exist due to such a phenomenon as contact potential difference. If two different solid conductors or semiconductors are brought into close contact with each other, then separated electric charges are formed in the vicinity of the place of their contact. In this case, at the external ends of these conductors a potential difference will occur. This potential difference will be equal to the difference in the work function for each metal divided by the electron charge.

It is clear that if you close such a pair into a ring, the resulting EMF will be zero, but if on the one hand it is still left open, then there will be a real EMF, ranging from tenths of a volt to units of volts, depending on what this is for the materials. Of course, it is not possible to measure the contact potential difference with a voltmeter, however, it will show itself on the current-voltage characteristic, for example, it manifests itself in a transistor and in a diode at the p-n junction ...

Hot water has become the norm in a modern house. In large cities, hot water is supplied centrally, while in the provinces people were either never heard of or had already forgotten. Even where there is a centralized hot water supply during the period of preventive maintenance, water can be turned off for a period of several days to several months. To create comfortable conditions and not depend on this factor, you need to install a water heater. In this article, we will consider the selection criteria and the design of a storage water heater.

Water heaters are by source of energy: gas, electric, other types of fuel. By type of heating and water movement: Flowing. For example, a gas water heater or an electric flow heater. In them, the water heats up when it flows through the heat exchanger. Cumulative. For example, a boiler, it is a water tank. In them, a certain amount of water is heated gradually. Heating time depends on power ...

Aluminum food foil and the finest copper wire, and between them - only 3 centimeters of air. The foil and wire are mounted on a square dielectric frame made of light plastic sticks. The design rests on the table, and like any object, gravity acts on it from the side of the Earth. But it is worth creating a potential difference of several thousand volts between the foil and the wire, applying a high constant voltage of about 30,000 volts from a low-power source to it, as the structure takes off, as if by magic.

We are not talking about a take-off capacitor, because the plates, if you can call them that at all, almost do not overlap each other in any significant fraction of their areas, which means that practically no energy accumulation in the dielectric between the "plates" occurs. If the structure did not hold the thinnest strong strings on the table, it would continue its progressive movement ...

Asynchronous motors are motors in the process of operation of which a sliding phenomenon is observed under load, that is, a “lag” of the rotor rotation from the rotation of the stator magnetic field. In other words, the rotation of the rotor does not occur synchronously with the rotation of the stator magnetization, but asynchronously with respect to this movement. That is why these types of motors are called asynchronous (non-synchronous) motors.

In most cases, pronouncing the phrase “asynchronous motor”, they mean the brushless AC motor.The slip value of an induction motor can be different depending on the load, as well as on the power parameters and the method of controlling the stator winding currents. If we are dealing with a conventional AC motor, such as AIR712A, then with a synchronous frequency of rotation of the magnetic field of 3000 rpm, under conditions of nominal mechanical load ...

Why are the wires of the power line humming? Have you ever thought about this? But the answer to this question can be by no means trivial, although completely unsophisticated. Let's look at several explanations, each of which has a right to exist.

Most often they bring such an idea. An alternating electric field near the power line wire electrifies the air around the wire, accelerates free electrons, which ionize the air molecules, and they in turn generate a corona discharge. And now, a corona discharge around the wire lights up and goes out 100 times per second, while the air near the wire heats up - cools down, expands - contracts, and in this way we get a sound wave in the air, which our ear perceives as a buzzing wire. Still there is such an idea. The noise comes from the fact that an alternating current with a frequency of 50 Hz produces an alternating magnetic field ...

To calculate the parameters of the charger for a particular battery, you must first take into account the type and parameters of the battery that you are going to charge with this device. The most important characteristics of a rechargeable battery are: capacity, full charge voltage, maximum allowable charge current, as well as a range of permissible operating temperatures.

Depending on what kind of battery it is, what type of materials it uses - the parameters of the charger should be selected individually. Here we look at lead-acid and lithium-ion batteries, or rather the features of their charging. The truth is that if the battery is always charged correctly, in compliance with the optimal values ​​of voltage and current, then it will retain its capacity for many charge-discharge cycles. Of course, provided that it is also discharged, subject to restrictions ...

If we take a brand-new lithium-ion battery, let us say size 18650, with a nominal capacity of 2500mAh, bring its voltage to exactly 3.7 volts, and then connect it to an active load in the form of a 10-watt resistor with a value of R = 1 Ohm, then what is the constant current we expect to measure through this resistor?

What will happen there at the very first moment of time, until the battery almost starts to discharge? In accordance with Ohm's law, it would seem that there should be 3.7A, since i = U / R = 3.7 / 1 = 3.7 [A]. In fact, the current will be slightly less, namely, in the region of I = 3.6A. Why is this going to happen? The reason is that not only the resistor, but the battery itself has some internal resistance, since the chemical processes inside it cannot occur instantly. If you imagine a battery in the form of a real two-terminal, then 3.7V - this will be its EMF ...

If you think carefully, then all kinds of applications for such a seemingly simple thing as an inductor simply can not be counted. In one article, we recall only a few of them. Meanwhile, human ingenuity and talent do not tire of creatively expressing themselves, inventing and developing more and more new devices and mechanisms based on inductors.

It would seem that here you can build? A simple coil of wire, it can be a core of a certain shape, and the current passing through the wire in a constant, variable or pulsed form.And meanwhile, without inductors all modern electrical engineering simply could not exist. Let's take a closer look. Elevator washers have been used worldwide for many years to load ferromagnetic waste. The electromagnet just clings to a crane hook ...