The discharge of current between people dressed in woolen clothes is surprising and amusing. To understand why this happens, you should familiarize yourself with what electrification of bodies is? Answers to emerging questions can be found in the physics section "Electrodynamics". It describes the principle of charge accumulation solids and the current laws of particle motion.
Highlights
To determine what electrification of bodies is, let’s consider the definitions and patterns of motion of charged particles. There are two opposite types: electrons (negative) and protons (positive) charges. When there is a huge accumulation of them, an electromagnetic field is formed. And the closer the static bodies are located to each other, the stronger the impact.
After the bodies come into contact, charges are exchanged and potentials are equalized (attraction or repulsion disappears). Particles of the same sign tend to move away, while particles of different signs attract each other. This can explain what electrification of bodies is: the mutual influence of electromagnetic fields created by electrons and protons.
Let's try to explain in simple language what electrification of bodies is: in order to form an electromagnetic field, you must first carry out an action that helps accumulate charge:
- friction;
- magnet influence;
- hitting an object;
- chemical reaction;
- attach a power source (at least a battery) to the object through the conductors.
There are many simple experiments that prove in practice the laws of electrodynamics.
Some evidence of patterns
As examples, you can conduct simple experiments for children:
- We take a regular flat comb, preferably a plastic one, but an iron one will do. We use hair or other natural things: a fur coat, a wig, a woolen scarf or a sweater. You need to intensively rub the cloves several times. Before this, the paper is finely crushed and then the electrified object is brought to it. The pieces instantly stick to the comb.
- can be done with an amber stone rubbed in a similar way. Afterwards, it can attract dry blades of grass and other objects. If you bring it to a thin stream of water, you will see how it deviates towards the stone.
Wool and silk fabrics
A glass rod is rubbed on a silk scarf. Afterwards, almost any small object can stick to it. This is clearly noticeable when we bring the tip to hair or thin strips of paper.
Objects made of ebonite are well electrified when rubbed against woolen fabric. And glass rods are rubbed with silk. However, these items produce different charges. Proof of this is the experience given below.
Ebonite rubbed with wool will repel silk. To see this, let's hang both objects on one thread and gradually bring them closer together so that they hang freely. As a result, we will see how the fabric begins to deviate to the side.
A similar phenomenon will occur during an experiment with a glass rod and wool. The electrification of bodies during friction actually occurs due to the transformation of one energy into another.
In everyday life
The electrification of bodies is constantly happening around us. When some objects rub, it becomes so high that even large heavy parts are attracted to them. At home, you can observe the electrification process as follows:
- We wear cloth house slippers, but not with rubber soles. Rub your feet on the carpet for a long time or wooden floor. And if you touch your fingertip with your partner, you will receive a shock. In the dark you will see how it sparkles.
- Often ungrounded refrigerators and washing machines also beat with static electricity. This was due to friction of the rotating parts.
- The palms become electrified after rubbing them against the same wool or silk. Clothes on a person attract all sorts of fluff and lint due to electrification. Girls remove it with antistatic sprays so that the skirt does not stick to their legs while walking.
For the same reason, televisions attract dust to the screens and body. A balloon IR, rubbed on the hair of the head, can be hung from the ceiling for a long time. The charged surface is attracted to the wallpaper or other covering.
Notation in electrodynamics
The letter q is used to classify and quantify the phenomenon of charged particles. Positive protons are indicated as - +q. Negative electrons received the symbol -q.
For calculations use total quantity charges. They are added or subtracted to obtain the true level of electrification of the item. In a quiet state, any level of particles is constant and has the form of the law of conservation of electric charge: q1+q2+...+qN= const.
And to calculate energy, the concept of “quantum” is used. In simple terms- This minimum quantity oppositely charged particles that can be transferred to another object per unit time. This level can be measured with a special device - an electrometer. Its operation is based on the accumulation of a charge by a metal arrow attached to fixed axis. As the level increases, the needle moves across the dial.
Features of calculations:
- Charges are acted upon by attractive forces. But they try to ignore them in the simplest calculations. After all, the particle sizes are very small compared to the distances covered.
- To determine the direction of movement of any selected particle, it is necessary to take into account all the forces acting from the surrounding elements. All calculations are carried out graphically: a vector diagram is drawn up.
How to define energy?
An electroscope is a device with which the electrification of bodies is recorded. The electric charge is accumulated by a metal rod in the form of petals mounted on a dielectric base - a plastic sleeve. The entire structure is placed in a steel case so that the moving part is located in front and covered with transparent glass.
To determine the charge level, you need to bring an electrified object to the top metal part of the device. The more particles pass, the more the petals diverge. The disadvantage of the design is the inability to record positive or negative values; all values are displayed without a sign.
Experimental Tools
To confirm electrodynamic forces, simple physical experiments using improvised means. Some of these will be:
- Two metal disks.
- A piece of woolen fabric to suit your size.
- Electroscope. Or your own invention: an example would be a metal rod connected by a conductor to one of the disks. The latter is installed horizontally. The rod is located vertically; finely cut pieces of paper can be placed at the base at a short distance.
You need to take one of the disks in your hand. Must use dielectric gloves. The second one has fabric laid on it.
Procedure
The essence of the experiment:
- The upper disk is tightly applied through the fabric to the lower one.
- It is turned several times and sharply removed upward.
- If everything is done correctly, the charge will be evenly redistributed between the disk and the rod.
- Pieces of paper will stick to the rod.
In order for the paper to fall, you can remove the charge simply by touching the metal part of the disk with your ungloved hand.
We have looked at the most common and most simple ways electrification of bodies
A macroscopic body can be given a charge of any sign. This process is called electrification. There are different ways electrification of bodies, that is, the transformation of electrically neutral bodies into charged ones; in particular, this can be done by rubbing bodies against each other (electrification by friction). For example, if you rub an inflated small balloon against wool, fur, or your hair, the balloon will stick to the body it was rubbed against. If you rub amber with a piece of cloth, it will attract light objects. The same can be observed if you rub an ebonite or glass rod with a cloth. In these cases, the object acquires an electric charge due to friction, that is, electrification by friction occurs, and the forces acting in this case are called electrical forces. Experiments show that two bodies, electrified by friction against each other, attract.
It is known that electrified ebonite and glass rods have various types charges. It was agreed to consider the charge that appears during electrification by friction on an ebonite rod or amber to be negative, and on a glass rod – positive.
Currently, the electrification of bodies is explained using the concept of the transfer of electrons from one substance to another. The outer electrons of the atoms of a substance are often very weakly attached to their nucleus and with friction, which ensures maximum contact between the surfaces of rubbing substances, they can move from one substance to another. A body that has received an excess of electrons becomes negatively charged. A body that has lost electrons is positive.
Table 1.1 shows the types of charges that arise in bodies when they are electrified by friction. The names of materials that are electrified by mutual friction are arranged line by line in different columns.
Table 1.1
In addition to electrification by friction, there is also electrification by induction. Let's consider it experimentally (Fig. 1.1). There are two uncharged metal balls.
Let's repeat the experiment with balls a little differently (Fig. 1.2). Take two uncharged metal balls touching each other (a). Let's bring the stick to the balls (b), then remove it and only after that move the balls apart (c). Surprisingly, now the balls will be uncharged (d).
If for the experiment we use not metal, but plastic or rubber balls, then we will not be able to electrify them by induction (that is, by action at a distance), no matter how far apart we use them!
 Rice. 1.3 |
Electrification by induction can be explained on the basis of the microstructure of the substance. In metals that belong to the class of conductors - substances that conduct well electric current, – there are free electrons that can move freely. When a charged body is brought to an uncharged metal ball, the electrons move either towards or away from the charged body, depending on the sign of its charge. In other substances, such as plastics or rubber, which are classified as insulators, neither positive nor negative charges can move freely. But when a body charged, for example, positively, is brought to a plastic rod, the configuration of the molecules of the rod is distorted in such a way that its surface facing the charged body will be negatively charged, and vice versa.
To detect electrified bodies, special devices are used - electroscopes. Appearance The device is shown in Fig. 1.3. The cylindrical body (1) is covered with glass (2). A metal rod (3) with easily movable petals (4) is inserted inside the device. The rod is separated from the metal body of the device by a plastic sleeve (5). When a charged body comes into contact with the rod of an electroscope, electric charges of the same sign are distributed along the rod and the arrow. Electric repulsion forces cause the needle to rotate through a certain angle, by which one can judge the charge transferred to the electrometer rod (Fig. 1.4).
 Rice. 1.4 |
Do the experiments!
1. Cut a strip of paper 1 cm wide from a notebook sheet. Having placed the strip on the notebook, run a plastic pen over it several times with light pressure. Then take the strip in one hand and the pen in the other and bring them closer together. The paper strip bends towards the handle, therefore, attractive forces arise between them.
Similar phenomena were known even before our era. For experiments on electrification by friction, they took amber and rubbed it with wool. After this, the amber and wool began to attract dry blades of grass. Amber in Greek means “electron”, and the word “electricity” comes from it.
Experiments show: electrified and non-electrified bodies always attract. Examples: a plastic stick and a thin stream of water, amber and dry blades of grass. Experiments also show that two bodies electrified by friction against each other always attract. For example, having become electrified by friction against our body, a sweater or skirt “sticks” to the body.
Electrified bodies (also called charged or having a charge) can not only attract; they can also repel. Let's conduct experiments. Rub an ebonite stick with a woolen mitten, and a glass stick with a silk scarf. By hanging the sticks on threads, we will see that ebonite and wool, as well as glass and silk, attract each other (see picture).
Now let's change pairs of bodies. We see that ebonite and silk, as well as glass and wool, repel each other (see picture).
There are other examples of repulsion of electrified bodies.
Previously, scientists did not distinguish between “glass”, “woolen”, “silk”, “ebony”, “amber” and other types of charges. However, in 1733, the French scientist C. Dufay carried out experiments and found out that only two types of charges can be formed on electrified bodies. This is how he wrote in his scientific works: “I call one kind glass electricity, the other resin electricity. A body electrified by glass electricity repels all bodies with glass electricity and attracts bodies with resin electricity.” Today we call two types of charges:
On the right is the symbol ±q – physical quantity electric charge. Electric charges are characterized by modulus and sign at the same time, expressed in special units, coulombs. We will learn how to measure charge and what 1 coulomb (1 C) is equal to in high school.
By repeatedly electrifying the same bodies, you can notice that the strength of their interaction can be different: greater or lesser. In physics, this is explained by the fact that the charge modulus can be large or small.
To detect charged bodies and compare their charges, an electroscope device is used (see figure). The metal body 1 is covered at the front with glass 2. A metal rod 3 with easily movable petals 4 is inserted inside the device. The rod is separated from the body by a round plastic sleeve 5. If the upper part of the rod is touched by a charged body, the petals will deviate from each other the more strongly, the greater the charge modulus of the body . Unfortunately, using an electroscope it is impossible to determine the signs of charges on bodies.
“Electrification of bodies” - Electrification. Electrostatic filters are used to purify the air. Electrization. Increased productivity, 50% paint savings. Amber is also rubbed against amber, against diamond, against glass and much more. Formation of ideas about electrification, about the interaction of charged bodies. comes from the Greek “elektron”, which means amber-yellow resin.
“Electric field charge” - Electrostatics. Point charge potential. There is no attraction or repulsion interaction. The voltage ratio at the ends of the first and second conductors is: 1) 1:4 2) 1:2 3) 4:1 4) 2:1. At what point in the field is the potential less? 1) 1 2) 2 3) 3 4) The potential is the same at all points of the field. Law of conservation of charge.
“Potential in Physics” - The ball was given a negative charge. Physics test “Electric field”. Question No. 5. The figure shows a cross-section of a solitary conducting hollow ball. Question No. 2. Question No. 4. In what areas of space is the field strength created by the ball different from zero? Which shows the field potential at a given point. Question No. 1.
“Electrification” - How do similarly charged bodies interact? And then they bring a metal ramp closer to the plane. Why do sparks appear and a cracking noise is heard when we take off a nylon shirt? Clothing made of synthetic fabrics, polymer and carpet floor coverings are electrified. Your hair will stand on end. Electrical phenomena in nature.
“Electric charge of the body” - M., 1992 Yavorsky B.M., Detlaf A.A. Physics course. Theoretical question and early exam completion 751 - 850 - two!! Questions and early passing of the exam 651 – 750 – three!!! OF Chernov I.P. Questions and passing the exam only on time, i.e. On schedule. Problem book in physics. Coulomb's law 1.3. Electrostatic field.
“Electric field strength” - In 1979, the highest voltage was obtained in laboratory conditions in the USA. Voltage characterizes electric field, created by current. Tension electric field. SI unit of voltage: [U] = 1 B 1 Volt is equal to electrical voltage in the section of the circuit where, when a charge equal to 1 C flows, work equal to 1 J is performed: 1 V = 1 J/1 C.
Have you noticed that when you take off a sweater or T-shirt, sparks fly and you hear crackling noises? What about when you get out of the car and get electrocuted? This is static electricity or electrification of bodies. It arises as a result of the accumulation of electrical charges of different signs on objects with their subsequent compensation. In this article we will briefly consider this phenomenon, the reasons for its occurrence, as well as methods of application both in everyday life and in industry.
Definition
Electrification is the process of separation of electrical charges and their accumulation in certain places of objects and bodies. The phenomenon occurs as a result of friction, contact of bodies or as a result of electrostatic induction. In simple words, when some object with an electric field is located nearby.
Let us remind you: in physics there are two types of charges - positive and negative, or protons and electrons. There arises between them. Like charges attract, and unlike charges repel.
The phenomenon is observed on power supplies and not only. Charges accumulate on dielectrics; everyone saw this in experiments illustrating the phenomenon with ebonite and glass rods, which were demonstrated in physics lessons at school.
Initially, all atoms, from which everything that surrounds us consists, are electrically neutral. As a result of the phenomenon of electrification, positive or negative charges appear on the surface of objects. Let us recall our school experience: if you rub an ebonite stick with a woolen cloth, after the rubbing stops the stick will remain charged. Then they say that the body is electrified.
Thus, during friction, electrons transferred from one object to another. As a result, after the cessation of friction, excess electrons remained “not on their own” bodies and an excess charge was obtained, and it ceased to be neutral. As a result of rubbing the stick against wool or fur, a negative charge was formed on its surface.
Conditions for the occurrence of the phenomenon and methods of charge transfer
We have told how this phenomenon in nature is explained, and now let's look at how bodies can be electrified. Let us immediately note that the fulfillment of all conditions is not necessary - electrification can occur for one reason or another, we will divide them into two main groups:
The first is mechanical interaction. During friction, the distance between objects is comparable to the distance between the molecules in it. Since the electrons in one of the bodies are weaker bound to the nucleus, they move “break out” to the other body. Other methods of electrification are impact and contact.
The second group is electrification by influence, that is, the phenomenon is observed when exposed to the body external forces, among which:
- Electric field. As a result of the influence of the field on the conductor, charges appear on its surface, and the smaller the bending radius of the surface, the more charges will accumulate here. This way there will be the most charges on the tip; we discussed this issue in more detail in the article and here
- Exposure to light. Discovered by Professor A.G. Stoletov in 1888, is that when zinc, aluminum, cesium, sodium, lead, potassium and other metals are exposed to light, they lose electrons and become positively charged.
- Warmth. When a metal is heated, electrons are given enough energy to escape the metal, resulting in it acquiring a positive charge.
- Chemical reaction. When there are two electrodes made of different metals, redox reactions occur, as a result of which one of them becomes positively charged and the other negatively charged. We discussed this in more detail in the article about.
- Under pressure. In piezoelectrics (quartz, Rochelle salt, ammonium phosphate), under mechanical action (compression or tension), positive and negative charges are formed on the faces.
These are the main types of electrification.
What laws of physics are associated with electrification?
The phenomenon of electrification is associated with such physical laws as:
- . Describes the force with which charges interact. In this way, you can determine how strongly electrified bodies are attracted to each other.
- . It says that algebraic sum charges in closed system unchangeable. This suggests that excess charges on electrified objects do not appear out of nowhere, but transfer from body to body.
We have already reviewed these laws; you can read more in the relevant articles to which we referred.
Application in practice
The phenomenon of electrification has both positive and negative manifestations. Examples of positive applications:
There are also a number of applications for cleaning, sorting, filtration, and in medicine to speed up treatment.
The negative impact of electrification can lead to fatal consequences:
- The occurrence of sparks when charged objects come into contact. Such cases include sparks in everyday life that jump when you take off your sweater, or when you get an electric shock when getting out of the car. For example, an airplane becomes electrified in flight, and when a ladder is connected to it, sparks can jump, and because of this, ignition is possible, so first remove the charge from the airplane. There have also been cases of oil tankers catching fire due to electrification.
- The phenomenon leads to the appearance of large electrical charges, which can lead to failure of electronic components in equipment, both during the production of equipment and during operation or repair. This occurs as a result of the tool discharging onto the PCB. Therefore, electronics repair technicians should work with grounded electrical wrist straps and grounded soldering irons and the like. In the modern element base there are a number technical solutions to minimize the impact of electrification on their operation. For example, installing Zener diodes in parallel with the GATE-SOURCE circuit of field-effect transistors.
Interesting! There is a known case when, when varnishing printed circuit boards After the installation of electronic components, there was a large rejection rate, despite the fact that all products were tested before varnishing. The question arose: how to get rid of the problem of electrification? The problem was solved by grounding the spray gun.
