Why is shocking clothing, furniture, car and surrounding objects

One of the reasons for this unpleasant phenomenon is explained very simply. Our body is very interesting in matters of electrical safety:

1. on the one hand, with our sensory organs we can’t recognize the presence of a nearby potential of electric voltage;

2. at the same time, if it falls under its action, we get unpleasant sensations, injuries, and tragic injuries.

In such situations, it is customary to say that we are shocked. Let's try to open this question in more detail, from the point of view of electrical engineering. We will need to take into account the nature of the current flow, the properties of our body, the experience of accidents accumulated by our predecessors, formulated by safety rules.

What is electric current?

He is called the ordered (oriented in a certain way) motion of the smallest particles with charges. It is created under the influence of the applied external forces of the electric field.

Charges are with a positive and negative sign. Only a negative sign is inherent in electrons. Holes in semiconductors have a positive charge, and ions in gases and liquids can have both signs. They are called so: anions and cations.

Electric current is created in all environments: solid, liquid and gaseous. Most often in practice we are faced with a current flowing in metals. We woke up in the morning, turned on the light, picked up the phone, opened the refrigerator, began to cook, went by car or trolley ... everywhere electricity works.

Carriers of charges in metals are electrons. They move, starting from the negative electrode and attracted to the positive.

The direction of current is considered to be the opposite movement to them.

In liquids and gases, in addition to electrons, ions act as carriers of electric charges, and the process of their formation, for example, associated with the heating of the air, is called ionization.

We can judge the flow of electric current by the following indirect signs:

1. the conductor is heating;

2. the chemical composition of the substance along which the charges move;

3. A force field is created that acts on nearby currents or magnetized objects.

Reasons for electric shock

The human body has a very complex set of substances, but it can be presented in a somewhat simplified way.

The amount of fluid in our body occupies approximately 60% of the total composition and depends on age. Children have the most moisture in the body, and with age its amount decreases and reaches 55% in older people.

These facts show that our body is a good vehicle. When it is between two different voltage potentials, a path is created through it for the electric current to flow in the liquid. Its size may slightly limit the slight resistance of the skin or clothing.

It is also necessary to take into account the physiological characteristics of the body. All types of muscles contract under the influence of signals from the central nervous system. For this, complex electrochemical transformations are involved. Extrusion of extraneous energy into these processes leads to serious damage.

Extraneous electric currents passing through a living organism heat the organs through which they flow, destroy the structure of physiological fluids, change the chemical composition of tissues, and damage the nervous system.

Particular danger is created by currents passing through the heart. They can cause it to fibrillate and stop.

And this can happen with a current of only 50 milliamps or 0.05 A.For comparison: an incandescent flashlight requires a load twice as much.

The most dangerous directions of currents through the heart are created when a person touches different potentials with two hands or forms contacts with his left hand and right foot. Electricians working under voltage, even with all means of electrical protective equipment, try to exclude working poses that allow the possibility of current flowing along these paths. (Work with your right hand, and keep your left in your pocket.)

Where does stress dangerous to humans come from?

In everyday life, and in production too, there are always two types of dangers:

1. static electricity;

2. a stationary electrical network that is energized.

It should be borne in mind that in the event of emergencies at remote sites, electric current can come to a person through the bypass current-conducting channels, for example, pipelines, fittings, metal structures.

The nature of static electricity

We constantly breathe air, are in its environment, consisting of various gases. The predominant charge carriers in it are positively and negatively charged ions. In order for them to begin to move (current began to flow), it is necessary to ensure their accumulation on certain objects and after that create a path for the discharge of dangerous potential.

In practice, such processes occur very often even without our participation in a completely natural way. The fact is that almost all substances in one way or another are able to concentrate charges of electricity on their surface.

It is well known that combing hair with plastic combs, as well as rubbing with an ebony stick on the wool, electrifies these objects or accumulates charges on them. This ability of physical substances is called the triboelectric effect. It is characterized by a special scale, an excerpt from which is given below.

 

 

Where do static charges come from?

As this diagram shows, wearing natural cotton clothing, using natural wood items and paper made from it eliminates the accumulation of electric charges on the human body. At the same time, work with leather, wool and plastic products leads to the accumulation of positive or negative potential.

It is worth putting warm wool socks on your feet in winter and walking a bit along the carpet or linoleum, as the high-voltage positive potential of static electricity is formed on the body. The same effect will ensure walking in ordinary slippers with rubber soles.

In winter, the air in the rooms is drier, and on our bodies we wear more clothes that cause static. Both of these factors contribute to increased charge accumulation in the cold season.

Plastic objects, and these are windows, various containers, foam insulation, collect negative charges.

The accumulation of potentials of charges contribute to:

• concrete slabs of building structures;

• increased dryness of air, characteristic of high-rise buildings in the winter.

In the normal state of rest of a substance, the charges tend to come into equilibrium. However, it is worth bringing them into motion: move, rotate, rub against each other with their surfaces, as the process of electrification begins. Other factors also cause it, for example:

• sharp heating and cooling items;

• irradiation from various electromagnetic energy sources;

• crushing, cutting into smaller parts.

During electrification, two processes occur simultaneously: the accumulation and runoff of charges. But, the first proceeds much faster and therefore prevails. Due to this, charges accumulate on the outer surface of the substance, form rather high potentials.

The industry produces devices that allow us to evaluate their value. Control measurements carried out by specialists showed the following figures:

• the potential of the body of a person walking in woolen socks on the carpet reached 6 kV;

• the body of a car driving on dry asphalt was charged up to 10 kV;

• a belt transmitting rotation between two pulleys in a mechanical drive has gained a potential of about 25 kV.

Such high voltage values ​​most often under normal conditions flow in small spark discharges, causing a decrease in performance, tingling, tingling of the skin, convulsive movements of the limbs. The low currents of such discharges are explained by the low power of the sources and the high electrical resistance of the air.

However, they can cause a fire in contact with a medium made from flammable liquids and gases.

In addition, static discharges pose a great danger to electronic equipment. They quite often damage field-effect transistors, microcircuits, and logic blocks highly sensitive to currents. It is enough to accidentally touch them, creating a path for current drainage, as this will cause damage to expensive equipment.

The charge of the high-voltage potential accumulated on a person’s clothes, through the total resistance of his body and the contact area, begins to flow off an impulse through the structure of semiconductor elements. In this case, the currents reach a maximum value in the first 10 milliseconds, and then they begin to gradually decrease.

The discharge current of such a pulse can not only cause obvious damage to electronic equipment when it completely loses its functionality, but also create hidden defects that slightly impair output parameters. In this case, the fine-tuned circuit is deregulated and its operation fails.

We conclude: it is necessary to avoid the accumulation of statistical charges and take measures to reduce their harmful effects.

Ways to reduce static discharge currents

The most affordable method is to increase the humidity in the room. It creates the best electrical conductivity of the medium, accelerates the flow of charges.

Therefore, maintaining optimal air humidity in living rooms with various humidifiers is one of the popular methods of combating static. The most budgetary option of this method is the placement of dampened fabrics on heating batteries, from which moisture evaporates.

The effect of static electricity can be reduced by treating the air with a special aerosol containing chemical reagents that improve the conductivity of the medium. They are sold in spray bottles or as liquids added during the washing process when rinsing the laundry.

Frequent airing of rooms also reduces dry air.

Shoes that we constantly wear on the street often have rubber or plastic soles. She well accumulates static charges when walking. To eliminate their influence allow special insoles made of natural materials.

However, the best result of the fight against static charges is provided by a properly organized potential equalization system, combined with the apartment ground loop. It is created once, and works constantly, relieving fatigue, normalizing pressure, and raising mood.

When repairing electronic equipment, use grounded bracelets, a set of antistatic clothing and shoes.

Static charges accumulating on the body of a moving car are removed with special “antistatic” belts, which are attached to the car body and create a chain of draining of dangerous potential to the ground.

However, such designs are not highly efficient; they partially solve their problem by removing only part of the dangerous charge. In order for them to work well, it is necessary to repeat the grounding of vehicles transporting flammable liquids, which is created by metal chains.

Therefore, leading car manufacturers integrate convenient devices into the car that allow them to remove the charge by performing mechanical actions on the controls when opening and closing doors, turning the steering wheel, and shifting the gear knob. They are shown in photos in light green.

Why is a stationary electric network shocking?

Electrical safety rules provide for all possible cases of preventing electric shock. They should be studied and put into practice.

However, in everyday life, a person violates them for various reasons, including ignorance. Therefore, we briefly consider the basic principles for the construction of automatic protections that ensure human safety in the home.

Circuit breaker protection

Modern machines are manufactured in a modular design to simultaneously perform two tasks:

1. the most rapid shutdown of the arising currents of short circuits, representing the greatest danger to humans;

2. elimination of network congestion that could damage equipment.

They are eliminated with a time delay.

For example, if a small child picks up two nails and plugs them into a live power outlet, then only a quick cut-off of the emergency current generated by the circuit breaker can save him.

In this case, the electrical outlet performs its intended purpose and bears an electric shock, and the machine saves the victim from a tragic outcome.

Leakage current protection

When damage to the electrical insulation of any household appliance occurs and the potential of the network falls on its conductive housing, a dangerous situation is created. A person accidentally touching damaged equipment beats an electric circuit along the circuit created by his body to the earth's contour.

The circuit breaker in most of these cases may not work, and the protection must be performed by an RCD or a difavtomat, which react to a violation of the current balance in the controlled circuit.

Lightning current protection

An accident associated with natural disasters can occur at any unfavorable moment in time. Protection against direct lightning strikes in the building is assigned to the lightning rod, hazardous discharge branch bus and ground loop.

If lightning enters the power supply house of the overhead line, then its huge potential can also pass into the dwelling. Protection in this case is assigned to arresters and SPDs.