Why is aluminum gradually removed from everyday life when installing electrical installations? Why is he bad and dangerous?

According to the requirements of the 7th edition of the Electrical Installation Rules (PUE), aluminum wires and cables with a cross section of less than 16 square meters. mm are not allowed for use during installation. But what is the reason for this? Why is aluminum so bad that has served the electricians faithfully for many years?

To answer these questions, you need to recall something from physics and a bit from the school chemistry course. What properties does aluminum have as a material? First of all, it is, of course, light. This is an undeniable advantage ...

Classification of grounding systems of electrical installations and modernization of apartment wiring. Application Experience.

For proper repair or modernization of wiring, you need to know exactly which grounding system is applied at the facility. Your safety depends on this, in addition, it is important when drawing up a reconstruction project. In some cases, for example, a three-core cable is used, and in others four and five-core cable.

The International Electrotechnical Commission and, with its submission, the 7th edition of the PUE (Electrical Installation Rules) distinguish 3 grounding systems and several of their subsystems. 1. TN system (subsystems TN-C, TN-S, TN-C-S); 2. TT system; 3. IT system ...

Physics of the process and practice of using reactive power compensation units

To understand the concept of reactive power, we recall first what is electric power.

Electric power is a physical quantity that characterizes the rate of generation, transmission or consumption of electrical energy per unit time.

The greater the power, the more work the electrical installation can do per unit of time. Measured power in watts (product Volt x Ampere). Instantaneous power is a product of instantaneous values ​​of voltage and current strength on a certain section of the electric circuit ...

Device application and classification of electromagnetic starters.

A magnetic starter is a device designed to control power loads. For example, electric heaters, electric motors, induction furnaces, etc. Naturally, the question arises, why can not you turn on and off the load using a circuit breaker?

The fact is that the resource of the machine for turning on and off is at least an order of magnitude smaller than that of a starter or contactor. In addition, the starter usually has a load current protection relay with the ability to adjust the current ...

A story about JK trigger and simple experiments to study his work.

In the previous parts of the article, triggers such as RS and D were described. This story will be incomplete if you do not mention the JK trigger. Like the D trigger, it has extended input logic.

In the 155 series, this is a K155TV1 chip manufactured in the DIP-14 package. Its pinout, or as they say now, the pinout (from the English PIN - pin) is shown in Figure 1a. Foreign analogues SN7472N, SN7472J.

The K155TV1 trigger has direct and inverse outputs. In the figure, these are conclusions 8 and 6, respectively. Their purpose is the same as for the previously considered triggers of type D and RS. Inverse exit begins in a small circle ...

The article describes the D-trigger, its operation in various modes, a simple and intuitive technique for studying the principle of action.

In the previous part of the article, the study of triggers was started. The RS trigger is considered the simplest in this family, which was described in the seventh part of the article.

D and JK triggers are more widely used in electronics devices. According to the meaning of the action, they, like the RS trigger, are also devices with two stable states at the output, but they have a more complex logic of the input signals.

It should be noted that all of the above will be true not only for K155 series microcircuits, but also for other series of logical microcircuits, for example, K561 and K176. All logic chips also work exactly ...

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) ...

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 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. ..