What do beginners need to know about electricity?
Readers who did not face works on electricity earlier often address us, but want to understand it. For this category the heading "Electricity for Beginners" is created.
Before starting the works connected with electricity it is necessary "to be grounded" a few teoreticheyosk in this question.
The term "electricity" means the movement of electrons under the influence of the electromagnetic field.
The main thing - to understand that it электричество is energy of the smallest charged particles which move in conductors in determinate direction (fig. 1).
The direct current practically does not change the direction and size in time. Let's say in the normal battery the direct current. Then the charge will overflow from minus to plus, without changing, will not run low yet.
Alternating current is current which with the certain frequency changes the direction of the movement and size. Provide current as water flow, teyokushchy on the pipe. Through some period (for example, 5 c) water will direct in one party, in another.
It happens to current hired quicker, 50 times a second (frequency of 50 Hz). Within one period of fluctuation the size of current increases to the maximum, then passes through zero, and then there is the inverse process, but already to other sign. On the question why so occurs and why such current is necessary, it is possible to answer that receiving and alternating-current transfer are much simpler, than constant. Receiving and alternating-current transfer are closely connected with such device as the transformer (fig. 2).
The generator which develops alternating current on the device is much simpler, than the direct current generator. Besides, on the long distance alternating current is suitable for transmission of energy best of all. With its help at the same time less energy is lost.
By means of the transyoformator (the spetsialyyony device in the form of coils) alternating current preobrazuyotsya from low tension on high and vice versa as it is presented on the illustration (fig. 3).
For this reason the majority of devices works from network in which alternating current. However the direct current is also applied rather widely: in all types of batteries, in chemical industry and some other areas.
Many heard such mysterious words as one phase, three phases, zero, grounding or the earth, and know that it is important concepts of the world of electricity. However not all understand that they designate and what relation have to surrounding reality. Nevertheless it is necessary to know it.
Without going deep into technical details which are not necessary to the house master, one may say, that the three-phase network is such way of transfer of electric current when alternating current flows on three wires, and on one comes back. The aforesaid should be explained a little. Any elektriyochesky chain consists of two wires. On one current goes to the consumer (for example to the teapot), and on another it vozyovrashchatsya back. If to open such chain, then current will not go. That's all description of the single-phase chain (fig. 4 A).
That wire on which current goes is called phase, or just the phase and on which returns - zero, or in zero. The three-phase chain consists of three phase wires and one return. It is possible because the alternating-current phase in each of three wires is shifted in relation to next on 120 ° (fig. of 4 B). In more detail the textbook on electromecanics will help to answer this question.
Alternating-current transfer happens through three-phase networks. It is favorable economically: two more zero wires are not necessary. Approaching the consumer, current is separated into three phases, and is given to each of them on zero. So it gets to apartments and houses. Though sometimes the three-phase network is brought directly to the house. As a rule, it is about the private sector, and such situation has the pluses and minuses.
The earth, or, is more correct to tell, grounding - the third wire in single-phase network. In effect, it does not bear the workload, and serves as some kind of predoyokhranitel.
For example, in the case when electricity gets out of hand (for example, the short circuit), there is the threat of the fire or electric shock. That it did not occur (that is the value of current should not exceed safe for the person and devices level), grounding is entered. On this wire the surplus of the elekyotrichestvo in a literal sense goes to the earth (fig. 5).
One more example. Let's say in operation of the electric motor of the washing machine there was the small breakdown and the part of electric current gets on the outer metal jacket of the device.
If there is no grounding, this charge and will wander on the washing machine. When the person touches it, it will become instant the most convenient exit for this energy, that is will receive electric shock.
In the presence of the earth wire in this situation the excessive charge will flow down on it, without having done anybody harm. In addition it is possible to tell that the zero conductor can also be grounding and, in principle, it and is, but only at power plant.
The situation when in the house there is no grounding, is unsafe. As to cope with it, without changing all wiring in the house, it will be told further.
Some handymen, relying on initial knowledge of electrical equipment, establish the zero wire as grounding. Never so do.
At break of the zero wire of the body of the grounded devices there will be energized 220 Century.Top