Hendrik Anton Lorenz. Biot-Savart-Laplace law. Ampère André-Marie. A magnetic field. Magnetic induction vector. Instructions for viewing. Lines of magnetic field induction. Hans Oersted. Graphic representation of fields. Induction of a magnetic field of rectilinear current. The direction of the magnetic induction vector. Mass spectrograph. Oersted's experience. Application. Ampère attended the meeting of the Academy. Modulus of magnetic induction vector.
"Energy Saving Program" - With respect to energy saving. Cracks in window frames. Energy Efficiency Improvement Program. Tap. Work in creative workshops. Color TV. Economic tasks. Debating club meeting. Smart consumption. Energy saving. Earth Hour. Energy consumption and its consequences. Energy problems of mankind. Rational use of energy. Fridge. Islands. Questionnaire.
""Newton's Laws" Grade 10" - The speed of the skier. The forces with which bodies act on each other. Check yourself. Galileo's principle of relativity. Non-inertial reference systems. Apple and Earth. Newton's laws. Find by construction the resultant of forces. Complete the summary table. Body acceleration. Reference systems. Dynamics. Swan. Features of the III law. The principle of superposition of forces. Speed directions. Inertia. body speed. The acceleration of a body is directly proportional to the force.
"IAEA" - Conflict. Areas of activity. Dwight Eisenhower. Atom for the world. Composition and organizational structure. Atomic Energy Agency. IAEA headquarters. A wide range of services. Control functions. Members. Creation of the IAEA. IAEA. Intergovernmental organization. Non-proliferation of nuclear weapons. Mohammed ElBaradei.
""Thermal engines" class 10" - Two-stroke engine. The main components of the engine. Compression ratio. Ivan Polzunov. Protection of Nature. Types of engines. Steam turbine. The engine runs on a four-stroke cycle. Thomas Newcomen. Danger. Diesel engines. Stages of development of the internal combustion engine. engine efficiency. Fiery heart. A bit of history. Pioneers of rocket and space technology. ICE cars have taken over the world. Preventive measures. The solution of the above problems is vital for a person.
"Electrolysis of electrolyte solutions" - Electric current in electrolytes. Obtaining chemically pure substances. Electricity. Decay of neutral molecules. First law of electrolysis. Charge. Application of electrolysis. Electrotype. Electroplating. electrolytic dissociation. Getting aluminium. Current source. Laws of electrolysis. Electroplating. Application. Electrolysis. Electric current in liquids. Anode. Cathode. NaCl.
The whole variety of natural phenomena is based on 4 fundamental interactions between elementary particles: strong, electromagnetic, weak and gravitational. Each type of interaction is associated with a certain characteristic of particles: for example, electromagnetic interaction with an electric charge. Electric charge is an inherent property of some elementary particles. Elementary particles will be called the smallest particles of matter known at the present time. All bodies in nature are capable of being electrified; acquire an electrical charge. The electric charge of a particle is its main characteristic. It has three fundamental properties:
The smallest unit of electric charge is called elemental charge.
The charge of all elementary particles (if it is not equal to zero) is the same in absolute value.
A positive elementary charge will be denoted by the symbol (+e), a negative - (-e).
Atoms and molecules of any substance are built from protons, electrons and neutrons. There are also known particles, called resonances, whose charge is 2e.
2) Any charge q is formed by a set of elementary charges, and is an integer multiple of e.
The electric elementary charge is very small, so we can consider the possible value of macroscopic charges to be continuously changing.
3) If a physical quantity can take only certain, discrete values, then we say that this value is quantized. Electric charge is quantized.
The amount of charge measured in different inertial frames of reference turns out to be the same. Its value does not depend on the frame of reference, and therefore does not depend on whether it is moving or at rest.
Electric charge is relativistically invariant. Electric charges can disappear and reappear. But 2 electric charges of opposite signs always appear or disappear. Electron and positron meeting annihilate, i.e. turn into neutral gamma photons, while the +e and -e charges disappear. If a gamma-ray photon enters the field of an atomic nucleus, then a pair of particles is born - an electron and a positron, and charges +e and -e arise.
The law of conservation of electric charge. It was established from a generalization of experimental data and experimentally confirmed in 1843 by the physicist M. Faraday.
Electrically isolated system we will call a system if there is no exchange of electric charges between it and external bodies. In such a system, new electrically charged particles can arise, but particles are always born, the total electric charge of which is equal to zero.
The algebraic sum of electric charges of any electrically closed system remains unchanged, no matter what processes take place inside this system.
where q 1 and q 2 are the charges of the bodies of the system before the interaction, and q 1 ¢ and q 2 ¢ - after the interaction.
The law of conservation of electric charge is related to the relativistic invariance of charge. Indeed, if the magnitude of the charge depended on its speed, then by setting in motion charges of one sign, we would change the total charge of an isolated system.
Since 1982, the SI system of units has been introduced in our country. The electric charge is denoted by the letters - q or Q. The SI unit for electric charge is Pendant,([q] = 1 C), pendant is a derived unit of measurement.
1 Pendant - this is an electric charge passing through the cross section of the conductor at a current strength of 1A for a time of 1 sec.
- [m], - [kg], - [sec], [ I ]-, - K ,
1Cl \u003d 2.998 10 9 CGSE units of charge; or 1СГСз = 1/3 10 -9 C, e = +1.6 10 -19 C.
CGSE system - (cm, g, s and CGSE unit of charge) is called the absolute electrostatic system of units.
CGSE unit of charge is such a charge that interacts in vacuum with a charge equal to it and located at a distance of 1 cm with a force of 1 din.
The elementary charge is equal to: e \u003d + 1.6 10 -19 C = 4.80 10 -10 CGSE - units of charge.
In SI, the unit of force is newton(H), 1H= 10 5 din.
Like the concept of the gravitational mass of a body in Newtonian mechanics, the concept of charge in electrodynamics is the primary, basic concept.
Electric charge is a physical quantity that characterizes the property of particles or bodies to enter into electromagnetic force interactions.
Electric charge is usually denoted by the letters q or Q.
The totality of all known experimental facts allows us to draw the following conclusions:
There are two kinds of electric charges, conventionally called positive and negative.
Charges can be transferred (for example, by direct contact) from one body to another. Unlike body mass, electric charge is not an inherent characteristic of a given body. The same body in different conditions can have a different charge.
Like charges repel, unlike charges attract. This also shows the fundamental difference between electromagnetic forces and gravitational ones. Gravitational forces are always forces of attraction.
One of the fundamental laws of nature is the experimentally established law of conservation of electric charge .
In an isolated system, the algebraic sum of the charges of all bodies remains constant:
|
q 1 + q 2 + q 3 + ... +qn= const. |
The law of conservation of electric charge states that in a closed system of bodies processes of the birth or disappearance of charges of only one sign cannot be observed.
From the modern point of view, charge carriers are elementary particles. All ordinary bodies are composed of atoms, which include positively charged protons, negatively charged electrons and neutral particles - neutrons. Protons and neutrons are part of atomic nuclei, electrons form the electron shell of atoms. The electric charges of the proton and electron modulo are exactly the same and equal to the elementary charge e.
In a neutral atom, the number of protons in the nucleus is equal to the number of electrons in the shell. This number is called atomic number . An atom of a given substance can lose one or more electrons or gain an extra electron. In these cases, the neutral atom turns into a positively or negatively charged ion.
A charge can be transferred from one body to another only in portions containing an integer number of elementary charges. Thus, the electric charge of the body is a discrete quantity:
Physical quantities that can only take on a discrete series of values are called quantized . elementary charge e is a quantum (smallest portion) of electric charge. It should be noted that in modern elementary particle physics, the existence of so-called quarks is assumed - particles with a fractional charge and However, quarks in the free state have not yet been observed.
In conventional laboratory experiments, electric charges are detected and measured using electrometer ( or electroscope) - a device consisting of a metal rod and an arrow that can rotate around a horizontal axis (Fig. 1.1.1). The arrowhead is insulated from the metal case. When a charged body comes into contact with the rod of an electrometer, electric charges of the same sign are distributed along the rod and the arrow. The forces of electrical repulsion cause the arrow to turn at a certain angle, by which one can judge the charge transferred to the rod of the electrometer.
The electrometer is a fairly crude instrument; it does not allow one to investigate the forces of interaction of charges. For the first time, the law of interaction of fixed charges was discovered by the French physicist Charles Coulomb in 1785. In his experiments, Coulomb measured the forces of attraction and repulsion of charged balls using a device he designed - a torsion balance (Fig. 1.1.2), which was distinguished by extremely high sensitivity. So, for example, the balance beam was rotated by 1 ° under the action of a force of the order of 10 -9 N.
The idea of measurements was based on Coulomb's brilliant guess that if a charged ball is brought into contact with exactly the same uncharged one, then the charge of the first will be divided equally between them. Thus, a method was indicated to change the charge of the ball by two, three, etc. times. Coulomb's experiments measured the interaction between balls whose dimensions are much smaller than the distance between them. Such charged bodies are called point charges.
point charge called a charged body, the dimensions of which can be neglected under the conditions of this problem.
Based on numerous experiments, Coulomb established the following law:
The forces of interaction of fixed charges are directly proportional to the product of charge modules and inversely proportional to the square of the distance between them:
Interaction forces obey Newton's third law:
They are repulsive forces with the same signs of charges and attractive forces with different signs (Fig. 1.1.3). The interaction of fixed electric charges is called electrostatic or Coulomb interaction. The section of electrodynamics that studies the Coulomb interaction is called electrostatics .
Coulomb's law is valid for point charged bodies. In practice, Coulomb's law is well satisfied if the dimensions of the charged bodies are much smaller than the distance between them.
Proportionality factor k in Coulomb's law depends on the choice of the system of units. In the International SI system, the unit of charge is pendant(CL).
Pendant - this is the charge passing in 1 s through the cross section of the conductor at a current strength of 1 A. The unit of current strength (Ampere) in SI is, along with units of length, time and mass basic unit of measure.
Coefficient k in the SI system is usually written as:
Where 
- electrical constant
.
In the SI system, the elementary charge e equals:
Experience shows that the Coulomb interaction forces obey the superposition principle:
If a charged body interacts simultaneously with several charged bodies, then the resulting force acting on this body is equal to the vector sum of the forces acting on this body from all other charged bodies.
Rice. 1.1.4 explains the principle of superposition using the example of the electrostatic interaction of three charged bodies.
The principle of superposition is a fundamental law of nature. However, its use requires some caution when it comes to the interaction of charged bodies of finite size (for example, two conductive charged balls 1 and 2). If a third charged ball is raised to a system of two charged balls, then the interaction between 1 and 2 will change due to charge redistribution.
The principle of superposition states that when given (fixed) charge distribution on all bodies, the forces of electrostatic interaction between any two bodies do not depend on the presence of other charged bodies.
Under normal conditions, microscopic bodies are electrically neutral because the positively and negatively charged particles that form atoms are connected to each other by electrical forces and form neutral systems. If the electrical neutrality of the body is violated, then such a body is called electrified body. To electrify a body, it is necessary that an excess or deficiency of electrons or ions of the same sign be created on it.
Methods of electrification of bodies, which represent the interaction of charged bodies, can be as follows:
- Electrification of bodies upon contact. In this case, with close contact, a small part of the electrons passes from one substance, in which the bond with the electron is relatively weak, to another substance.
- Electrization of bodies during friction. This increases the contact area of the bodies, which leads to increased electrification.
- Influence. Influence is based phenomenon of electrostatic induction, that is, the induction of an electric charge in a substance placed in a constant electric field.
- Electrification of bodies under the action of light. This is based on photoelectric effect, or photoelectric effect when, under the action of light, electrons can fly out of the conductor into the surrounding space, as a result of which the conductor is charged.
Numerous experiments show that when body electrification, then electric charges appear on the bodies, equal in magnitude and opposite in sign.
negative charge body is due to an excess of electrons on the body compared to protons, and positive charge due to a lack of electrons.
When the electrification of the body occurs, that is, when the negative charge is partially separated from the positive charge associated with it, law of conservation of electric charge. The law of conservation of charge is valid for a closed system, which does not enter from the outside and from which charged particles do not go out. The law of conservation of electric charge is formulated as follows:
In a closed system, the algebraic sum of the charges of all particles remains unchanged:
q 1 + q 2 + q 3 + ... + q n = const
where q 1 , q 2 etc. are the particle charges.
Interaction of electrically charged bodies
Interaction of bodies, having charges of the same or different signs, can be demonstrated in the following experiments. We electrify the ebonite stick by rubbing against the fur and touch it to a metal sleeve suspended on a silk thread. Charges of the same sign (negative charges) are distributed on the sleeve and ebonite stick. Approaching a negatively charged ebonite rod to a charged cartridge case, one can see that the cartridge case will be repelled from the stick (Fig. 1.2).
Rice. 1.2. Interaction of bodies with charges of the same sign.
If we now bring a glass rod rubbed on silk (positively charged) to the charged sleeve, then the sleeve will be attracted to it (Fig. 1.3).
Rice. 1.3. Interaction of bodies with charges of different signs.
It follows that bodies with charges of the same sign (like charged bodies) repel each other, and bodies with charges of different signs (oppositely charged bodies) attract each other. Similar inputs are obtained if two sultans are brought closer, similarly charged (Fig. 1.4) and oppositely charged (Fig. 1.5).
The fact that electric charges exist in nature has been known to mankind since the time of the ancient Greek natural philosophers, who discovered that pieces of amber, if rubbed with cat hair, begin to repel each other. Today we know that electric charge, like mass, is one of the fundamental properties of matter. Without exception, all the elementary particles that make up the material Universe have one or another electric charge - positive (like protons in the composition of the atomic nucleus), neutral (like neutrons of the same nucleus) or negative (like electrons that form the outer shell of the atomic nucleus and provide its electrical neutrality as a whole).
One of the most useful techniques in physics is to identify the total (total) properties of a system that do not change with any changes in its state. Such properties, expressed in scientific language, are conservative, because for them conservation laws. Any conservation law is reduced to a statement of the fact that in a closed (in the sense of the complete absence of "leakage" or "inflow" of the corresponding physical quantity) conservative system the corresponding quantity characterizing the system as a whole does not change with time.
Electric charge just belongs to the category of conservative characteristics of closed systems. Algebraic sum of positive and negative electric charges − net net charge of the system- does not change under any circumstances, no matter what processes take place in the system. In particular, during chemical reactions, negatively charged valence electrons can be redistributed in any way between the outer shells of atoms of various substances that form chemical bonds - neither the total negative charge of electrons nor the total positive charge of protons in the nucleus in a closed chemical system will change. And this is just the simplest example, since during chemical reactions there is no transmutation of the protons and electrons themselves, as a result of which the number of positive and negative charges in the system can simply be counted.
At higher energies, however, electrically charged elementary particles begin to interact with each other, and it becomes much more difficult to follow the law of conservation of electric charge, but it is also fulfilled in this case. For example, in the reaction of spontaneous decay of an isolated neutron, a process occurs that can be described by the following formula:
where p is a positively charged proton, n is a neutrally charged neutron, e is a negatively charged electron, and v is a neutral particle called a neutrino. It is easy to see that both in the starting material and in the reaction product the total electric charge is equal to zero (0 = (+1) + (-1) + 0), however, in this case, there is a change in the total number of positively and negatively charged particles in the system. This is one of the radioactive decay reactions in which the law of conservation of the algebraic sum of electric charges is fulfilled despite the formation of new charged particles. Such processes are typical for interactions between elementary particles, in which particles with one electric charge give birth to particles with other electric charges. The total electric charge of a closed system, in any case, remains unchanged.
