Many living organisms behave like electric dipoles. Electric dipolem. They call the system of two equal charges of the opposite sign, located at a distance of L from each other. The vector spent from the negative charge to the positive is called shoulder dipole. The main characteristic of the dipole is an electric dipole moment - vector physical quantityequal to the product of the module of one of his charges on the shoulder The electrostatic field is potential. This means that the work on the movement of charge in the electrostatic field does not depend on the form of the trajectory, which moves the charge, but is determined only by the initial and ending position of the charge. For any charge, placed in an electrostatic field, the force acts that can move it. Any electrical charge located in the electrostatic field has some potential energy. Therefore, work A, performed when moving electric charge From one point of the field to another equal to the potential energy W of this charge A \u003d W 1 - W 2 where W 1 and W 2 are potential charges of charge in the initial and endpoints, respectively. The most important energy characteristic electric field is the potential. Electric field potential φ is called a scalar physical quantity, numerically equal to the potential energy of a single positive charge

Placed at this point From this formula

follows a capacity of potential - volt (B): 1B \u003d 1 J / CL. Under the action of the forces of the field, a positive charge will strive to move from a point with a higher potential to a point with a lower potential, and a negative charge on the contrary. Numerical value and potential sign depends on the selection of the zero level. In physics, it is usually believed that the potential is zero at infinity. In practice in electrical engineering, for zero potential, the potential of the surface of the earth or conductor connected to the ground is usually chosen. When calculating it is important to know not the absolute values \u200b\u200bof potentials, in any two points of the field, and the difference of potentials Δφ. Potential difference It is determined by the following expression Δφ \u003d φ 1 - φ 2 where φ 1 is the potential of the point 1, φ 2 - the potential of the point 2. When the charge q is moved from one point of the electric field to another, the operation is performed a \u003d q (φ 1 - φ 2) of the body In which electrical charges can be moved, called conductors. The transfer of charges in the conductors of the first kind (metals) is due to the movement of electrons, the second kind (gases and liquids) by the movement of ions. In dielectrics, the movement of electrical charges is impossible. The electrostatic field is a special kind of matter, fills all the space surrounding the restricted charges. Charges caused by excess or disadvantage of electrons in each element of the amount of charged body are called free. Charges caused by the polarization of the dielectric are called connected. The potential of this field of the field is the value equal to the work performed by the field with the movement of a single positive charge from this field point to infinitely remote. The potential difference between two points is determined by the work performed when moving a single charge between these points. Equipotential surface is a geometric location of constant potential points.

35.Electility. Condencators. Value FROM called electrical capacity of the conductor. Electrical capacity characterizes the ability of conductors to accumulate electrical charges. Unit of electrical capacity is farad (F) The capacity of such a secluded conductor, to whom the charge of 1 CL reports the potential of 1 to: 1F \u003d 1kl / c. 1 Farad is a very large electrical capacity. EarthFor example, has an electrical capacity of ≈ 711 μF. However, scientists have created devices that are capable of accumulating a fairly large electrical charge with relatively small sizes. They got a name - condencators. The condenser consists of two conductors located at a short distance from each other, separated by a dielectric layer. The exchange processes that are continuously occurring in a living organism lead to the redistribution of charges in the tissues and the emergence of potential differences mentioned biopotentials.To date, it is established that all cells of animals and plant organisms have one or another type of electrical activity. Electrotrix - the phenomenon of the occurrence of stresses in the dielectric under the action of the electric field. The body's electrical capacity is a physical value equal to the number of electricity that increases the potential of this body per unit. Body serve to accumulate electrical charges are called condensers. The condenser is a passive electronic component. It consists of two electrodes in the form of plates separated by a dielectric. Condenser in chains direct current It can carry out current at the time of its inclusion in the chain, at the end of the transient process, the current through the capacitor does not flow. In the chain of the same aCand it conducts vibrations of alternating current by means of cyclic recharging of the condenser, closing the so-called shift current.

36. Electrostatic protection.The electrostatic field is a special kind of matter, fills all the space surrounding the restricted charges. Property - transferring the action of one electrical bodies to others; Such an action is manifested in the emergence of forces between charged bodies. Spot charges are such charged bodies whose dimensions are small compared to the distance between them. Each point electrostatic field characterized by tension. Vector electrostatic induction There is a magnitude proportional to the vector of the electrostatic field intensity, and the proportionality coefficient is the dielectric constant The medium showing how many times the electric field strength in the dielectric is smaller than the field strength in vacuum.

37. Current power. EMF. TensionThe tension is a physical value proportional to the strength with which the field is valid for a single positive charge; Direction of tension vector coincides with the direction of the strength vector. Measured in V / m, N / CL. Line of tension is a line, at each point of which the vector of tension characterizing this point is directed by the tangent of the line under consideration. Tension lines come out of a positive electric charge and are included in negative or go into infinity. The number of tension lines is called a stream of tension through the surface. The strength of the current flowing through this conductor site is a physical value measured by the number of electricity tolerable through this platform per unit of time. It is measured in A. Electric current, the value of which does not change in time, is called constant. Electrical power source electric current It is the value defined as the algebraic amount of the potential jumps encountered when bypassing the circuit in which "only this source of the current is included. It is equal to the potential difference on the clips of the open source. Electric shockthe directional movement of electrically charged particles is called. For the direction of current, it is considered to refer to the direction of movement of positive charges. Basic characteristic

electric current is current I., numerically equal

charging flowing through the cross section of the conductor

per unit time: Unit measuring current in si

is an ampere (a): 1A \u003d 1kl / s. If the current and its direction is not changed over time, such a current is called constant. First prerequisite The existence of electric current is the presence of the potential difference Δφ is not zero. To maintain it, a special device is needed, with which the separation of charges at the ends of the conductor will occur. Such a device is called the generator or current source. Galvanic elements, batteries, thermoelements, photo cells, etc. are used as the current source. The current source simultaneously performs the second condition of the electric current - it closes the electrical circuit, which could be carried out by the continuous movement of charges. The current flows through the outer part of the chain - the conductor and internal - the current source. The current source has two poles: positive (+) with higher potential and negative (-) with lower potential. In the negative pole, an excess of electrons is created, and in positive - disadvantage. The separation of charges in the current source is produced using the forces having non-electrical nature (mechanical, chemical, thermal, etc.), since electrical forces can only be connected, but not separating multi-dimensional charges. Therefore, these forces are called third parties, the work of a third-party force on the separation of charges is equal to: a \u003d and the East + A "where A East \u003d Q (φ 1 - φ 2) work against the power of the electric field; a" - the work performed against the mechanical strength of resistance of the medium Source. The work performed by a third-party force on moving along this section of a single positive charge chain is called electromotive power (EMF) and denotes ε. IN

particular for the current source: For the current source, we get:

If the source pole is open,

that and "\u003d 0 and ε \u003d φ 1 - φ 2 i.e. EMF of the current source with an open external circuit is equal to the potential difference, which is created on its poles.

Potential difference on the poles of the current source, closed external electrical chain called voltage source U. voltage current source less emf

by magnitude: In addition, on any plot

the external electrical circuit there is a certain potential difference, it is called a voltage drop (voltage) U in this section, the voltage and EMF are measured as well as the difference in volt potentials.

38.To in metals.In metal, the current occurs due to the directional movement of the electrons existing in it in the free state in the form of electronic gas. Electric current in metals is an ordered movement of electrons under the action of an electric field. When current flows over the metal conductor of the substance, the substance does not occur, the metal ions do not participate in the transfer of the electric charge. All metals in solid and liquid state are electrical current conductors. When the electric current is passed, the mass of metallic conductors remains constant, does not change and their chemical composition. Under the action of an electric field, free electrons, except for chaotic movement, acquire an ordered movement in one direction, and electric current occurs in the conductor. Free electrons face ions crystal lattice, giving them with each collision kinetic energy. As known carriers of charges in metals are free electrons. Thus, the current in metal conductors is the directional motion of free electrons (despite the fact that the direction of the current is taken direction of movement of positively charged particles). Back in 1826, the German physicist ohm emphasized that the current of the current in the conductor is proportional to the voltage U between the sections of the conductor: i \u003d ku where k is the proportionality coefficient called electrical conductivity or conductivity

explorer. Value reverse conductivity called

electrical resistance Explorer. Then law

Ohm for a circuit site (no current source). The unit of measurement of resistance was named OM. From it follows that: 1 ohm \u003d 1 V / and the current resistance to the metal conductor is due to the collision of free electrons with metal ions. It depends on

forms, sizes and substances of the conductor: Where L - Length

explorer, S - The area of \u200b\u200bits cross section, ρ is a specific resistance, the proportionality coefficient characterizing the material from which the material is made. unit of measurement specific resistance Om · m. Experience shows that the current always causes some heating of the conductor. Heating is due to the transition kinetic energy Moving on the conductor of electrons with the ions of the crystal lattice in heat. This amount of heat is determined by the law of Joule - Lenza where I is the current of the current in the conductor, R is the resistance, T is the passage time through the conductor. It is on the thermal action of the current that the operation of incandescent lamps, electric furnaces, electric welding, household electric heating devices, etc.

39.t in fluids. Current in gases.Electric current in liquids. The electric current is carried out solutions of many substances in water. Clean water does not conduct an electric current, there are no free carriers of electrical charges. Do not conduct electric current and crystals of the table salt, sodium chloride. When the electric current is passed, chemical changes occur, as a result of which gas is released. The conductors of the second kind are called electrolytes, and the phenomenon occurring in the electrolyte when the electric current is passed through it - electrolysis. Metal plates, lowered in electrolyte, are called electrodes; One of them, connected to the positive pole of the current source, is called an anode, and the other, connected to the negative pole, is a cathode. Particles of the molecule having an electric charge are called ions. The phenomenon of electrolysis was opened in 1837 B. S. Jacobi, who made numerous experiments on the study and improving the chemical sources of current. Jacobi found that one of the electrodes placed in a solution of copper sulfate when the electric current passes through it is covered with copper. This phenomenon called by galvanoplasty, for example, the coating of metal objects with a thin layer of other metals - gilding, silvering. Electric current in gases.

In the gases there are unhappiecked and independent electrical discharges. The phenomenon of the flow of electric current through the gas is called an independent electrical discharge. The process of separation of an electron from an atom is called an atom ionization. The minimum energy that needs to be expensive for the separation of an electron from an atom is called ionization energy. Partially or completely ionized gas, in which the density of positive and negative charges The same, called plasma. Electric current carriers with poor discharge are positive ions and negative electrons. Spark discharge It occurs between the two electrodes charged different charges and having a greater potential difference .. Spark discharge short-term, its mechanism is an electronic shot. Lightning is the type of spark discharge. Between the wire of the power line and the surface of the earth, there is a special form of self-discharge in gases, called crown discharge. Electric current carriers in the arc are positively charged ions and electrons. Discharge occurring under reduced pressure is called glow discharge

40.Magnetic field and its characteristics. In the space surrounding the electric current, the magnetic field occurs. It is manifested by the forces acting on the conductors made in it with the current. The magnetic field is created only by moving charges and acts only on the electrical charges moving in this field. The magnetic field is characterized by a magnetic induction vector. The induction of the magnetic field is the value equal to the moment of forces acting on the frame with a current having a single magnetic moment. Unit of measurement of the induction of the magnetic field - Tesla (TL). The magnetic field is vortex (the operation performed when bypassing the charge of the current on the closed path is not zero). The magnetic field of the direct permanent magnet is similar to the magnetic field of the solenoid (the power lines come out from the North Pole and are included in the south). The magnetic properties of some iron ores (the ability to attract iron objects) are known with deep antiquity and obtained use in a magnetic compass device. It turned out that a permanent magnet has two poles - northern (denotes the letter N) and south (denotes s). Motionic magnet poles are mutually attracting, and the same is repelled, an idea of \u200b\u200bexistence has arisen in science. magnetic charges (positive and negative). It is impossible to divide the poles of the magnet. In 1820, the Danish physicist Ersted found that the wire for which electric current flows on the magnetic arrow located near it. The magnetic arrow turns perpendicular to the wire, the French ampere physicist discovered the magnetic interaction of two conductors with a current around moving electrical charges (electric currents) Another type of field occurs - a magnetic fieldis generated by moving electric charges and an alternating electric field. Magnetic field is power field - It acts with some force on moving charges, conductors with current, permanent magnets, are depicted graphically by silest lines. The power lines of the magnetic field are always closed they have no beginning, no end. Therefore, the magnetic field is vortex. The tangent to the magnetic power line at any point coincides in the direction with the so-called magnetic induction vector. Therefore, the power lines of the magnetic field are typically called magnetic induction lines. Vector magnetic induction - Main power characteristic Magnetic field: proportional to power that acts on the northern end of an infinitely small magnetic arrow placed in

this magnetic field point. The unit of magnetic induction is Tesla (TL): Induction (with other things being equal) depends on the properties of the medium (substance). Induction in substance and induction in vacuum are related to the following relationship where μ is magnetic permeability of the substance, dimensionless physical quantity characterizing the magnetic properties of the medium. For vacuum μ \u003d 1. Along with the induction, there is another characteristic of the magnetic field - the tension associated with magnetic induction by the ratio where μ 0 is a magnetic constant, depending on the selection of the system of units. It does not have physical meaning as well as ε 0 in electrostatics. In the international system units The value does not depend on the properties of the medium and is the characteristic of the magnetic field created by external with respect to the sources under consideration. Unit of measuring the tension of the magnetic field - a / m.

41. Ampere Law- The law of interaction of permanent currents. Andre Marie Ampera is installed in 1820. From the AMPER law it follows that parallel conductors with constant currents flowing in one direction are attracted, and in the opposite - repel. The AMPER's law is also called the law that determines the force with which the magnetic field acts on a small segment of the conductor with a current. F \u003d BI. l.sINA (A is the angle between the current direction and the induction of the magnetic field). This formula of the Ampere Law turns out to be fair for a straight line conductor and uniform field. If the conductor has an arbitrary formula and an inhomogeneous field, then the amper's law takes the form: DF \u003d I * B * dlsinaThe ampere force is directed perpendicular to the plane in which the DL and B vectors lie to determine the direction of force acting on the conductor with a current placed in the magnetic field, the rule of the left hand is applied. The direction of force is determined by the rule of the calculation of the vector product, which is convenient to remember using the rule of the right hand. Ampere Module can be found by the formula:

42.Magnetic properties of substances. Nature of magnetism.The substance capable of influence the magnetic field is called a magnet. The molecular current is a circular current, flowing into molecules of substance. Molecular currents exist in molecules and are excited under the action of an external magnetic field. The appearance in the substance of an additional magnetic field under the action of an external magnetic field is called magnetization. The magnetization will be the magnitude characterized by the medium magnetization and the unit of its volume is equal to the magnetic moment. The ratio of the magnetization vector to the vector of the external field tension is called the susceptibility of the magnetic. Substances, the field of magnetization of which is determined by the orientation of the molecular currents existing in molecules are called paramagnets. Diamagnetics This substance in which the magnetization field is determined by currents arising from the resulting molecular currents under the action of an external field. Substances in which the field of magnetization occurs by orientation of magnetization domains is called ferromagnetic. The magnetic properties of some iron ores (the ability to attract iron objects) are known with deep antiquity and received the use of more than a thousand years before our era in the magnetic compass device. It turned out that a permanent magnet has two poles - northern (denotes the letter N) and south (denotes s). The Northern Pole magnet, which is given the opportunity to freely navigate, turns to the north, and southern - to the south, the variety of magnets are mutually attractive, and the same are repelled. As a result, in science an idea of \u200b\u200bthe existence of magnetic charges (positive and negative), two new magnets always turn out of the cut magnet. It is impossible to divide the poles of the magnet. In 1820, the Danish physicist Ersted found that the wire for which electric current flows on the magnetic arrow located near it. The magnetic arrow rotates perpendicular to the wire. At the same time, the French ampere physicist discovered the magnetic interaction of two conductors with a current (mutual attraction or repulsion depending on the direction of currents flowing into them). Subsequent experiments have shown that the magnetic properties have a current in liquids, gases, any moving electrical charge. Thus, it turned out that there is another type of field around moving electrical charges (electric currents) - a magnetic field. No magnetic charges exist, the magnetic field is generated by moving electric charges and an alternating electric field. The magnetic field is a power field - it acts with some force on moving charges, conductor with current, constant magnets. Since the magnetic field is a power field, it is depicted graphically by means of power lines as well as an electric field. The power lines of the magnetic field are always closed they have no beginning, no end. Therefore, the magnetic field is vortex.

43.Thenage charged particles in a magnetic field. The Lorentz power is the force acting on a charged particle when it moves in a magnetic field. The ratio of the charge of a particle (electron, ion) to its mass is called a specific charge of this particle. Knowing the direction of Lorentz's force and the direction of the charged particle caused by it in a magnetic field can be found a sign of the charge of particles that move in magnetic fields.
If the charged particle in the magnetic field moves with a velocity V along the magnetic induction lines, the angle α between vectors V and B is 0 or π. Lorentz's power is zero, i.e. the magnetic field on a particle does not act and it moves evenly and straightly. If the charged particle moves in a magnetic field with a velocity V, which is perpendicular to the vector B, then the Lorentz force f \u003d q is constant in the module and perpendicular to the particle path. According to Newton's second law, Lorentz's strength creates a centripetal acceleration. It means that the particle will move around the circumference. The period of rotation of the particle, i.e. the time T, for which it makes one full turn. As well as on the conductor with a current, the magnetic field is valid for a separate charge moving in it. The process of interaction of moving charges with an external magnetic field was studied by Danish physicome Lorenz. As a result of the generalization of the experimental data, it derived a formula for calculating the force acting from the magnetic field to a moving charged particle. This force was named lorentz power: where q is a particle charge, V is its speed, B is a magnetic induction, α is the angle between vectors and. Being perpendicular to the speed, the Lorentz power changes only the direction of the speed of the particle and does not change its magnitude. If the particle flies into a homogeneous magnetic field parallel to the magnetic induction lines, it continues to move in a straight line at the initial speed (α \u003d 0, sinα \u003d 0 and therefore f l \u003d 0). If the vector of the initial velocity of the particle is perpendicular to the magnetic induction lines, then in this field, the particle will move around the circumference of some radius with a constant period. In this case, the period of circulation depends only on the specific charge of Q / M particles. If the particle flies into a homogeneous magnetic field under a certain angle α to the magnetic induction vector, then its trajectory is a screw helix. Features of the movement of charged particles in magnetic and electric fields are widely used in modern techniques. They underlie the operation of the radar, electron microscope, televisions and monitors with electronolic tubes, accelerators of charged particles, etc. The mass spectrometry is based on the same physical phenomena - the method of determining the masses of particles and their relative content in complex substances, which is widely used in chemistry and biology.

44. Equating electromagnetic induction.The phenomenon of the occurrence of electric current in a closed conductive circuit when changing the magnetic induction flow through the area limited to this circuit is called electromagnetic induction. The current current is called induction. The induction current has such a direction that the magnetic induction stream created by it compensates for the change in the flow of magnetic induction, which caused this current. Electromotive force

(EMF) induction current is called EMF induction. It is proportional to the change in the flow of magnetic induction in time.

45.The induction and self-induction.The occurrence of induction emfs in the circuit, due to the change in current in the same circuit, is called self-induction. Self-induction currents occurring in conductors when the electric current is turned on and turned off, they are referred to as the closure and opening extracts. The property of the contour has more or less pronounced self-induccus is characterized by self-induction coefficient. The self-induccus coefficient is equal to self-induction EMF, which occurs in the circuit when the current changes in it per unit per unit of time. The appearance of the induction current in the circuit caused by the change in the electric current in the adjacent circuit is called mutually induction. It is characterized by a mutual induction coefficient, which is determined by the geometric shape, size and mutual position of the contours, and in the presence of ferromagnetic bodies and the power of the current in the circuit. Induction currents arising in solid conductors who cannot be considered as linear contours are called Foucault currents. The phenomenon of self-induction of Foucault currents in the conductors for which alternating current flows is called the skin effect.

46. \u200b\u200bAlternating current.Alternating current is a current, whose value changes over the law of cosine or sinus. AC current, the value of which at every given time is the same for all sections of the chain under consideration, is called a quasistationary. Constant current resistance is called ohmic or active. Electrical circuits have alternating current inductive and capacitive resistance due to the presence in these circuits of capacitors and inductors of inductance. Inductive resistance is equal to the product of the circuit inductance per circular current frequency, capacitive resistance is inversely proportional to the product of the tank to the frequency of the current. The resistance exerted by the electrical circuit of the variable current is called the impedance of the chain.

Effective AC power is equal to DC power, the thermal action of which is equivalent to the action of the alternating current under consideration

47. The concept of an electromagnetic field. Electromagnetic waves.The presence of electrical oscillations in the oscillatory circuit causes a magnetic field in the surrounding space in the surrounding space. Electric I. magnetic fieldarising from electrical oscillations exist inextricably come from each other and are called electromagnetic field. The electromagnetic field that occurs in any place of space, over time applies to all other parts of the space, if it changes periodically, then these changes are transmitted to the surrounding space. This is called an electromagnetic wave. In the electromagnetic wave, the vectors of the electric and magnetic fields, as well as the vector indicating the direction of the propagation of the wave, are mutually perpendicular. Such a wave is called transverse. Electromagnetic waves are used for wireless transmission of various signals, which is used in radio engineering, television, radar.

48. Electric oscillations.Machines serving for electricity by using electromagnetic phenomena are called generators; They convert mechanical energy into electric. Machines converting electrical energy into mechanical, are called electric motors. The oscillating circuit is a closed chain consisting of a container, inductance and inevitably present ohmic resistance in which electrical oscillations can occur. Electric oscillations in such a circuit are performed due to the transitions electrical Energy Condenser in magnetic energy inductance coil. The presence of electrical oscillations in the oscillatory circuit causes a magnetic field in the surrounding space, which is vortex.

49 On the nature of light.The light simultaneously has wave and corpuscular properties. It extends in the form of short electromagnetic waves. The energy of the wave particles (a quantum of light or photon) is proportional to the frequency of light. The ratio of proportion is the constant plank. Photon energy decreases with a reduction in frequency. The speed of light in emptiness does not depend on the state of the speed of reference systems. It is a universal global constant C \u003d 3.8 × 10 -8 m / s. Papping on the border of the section of two media, the light beam is partially reflected, partially passes into a new medium (refracted). The angles compiled by the norm conducted to the interface of the media, with the incident, reflected and refracted rays, are called respectively angles of falling, reflection and refraction.

50. Recovery and refraction of light.The ratio of the sinus of the angle of falling to the sinus of the refractive angle is called the relative indicator of the refractiveness of the substance. If the beam originally spread in emptiness, then the refractive index is called absolute. The optical density of the substance determines its refractive index. The phenomenon consisting in the reflection of the entire energy incident on the border (there is no refracted beam) is called the phenomenon of complete internal reflection. It occurs when light passes in an optically more dense medium on the border with an optically less dense medium. The angle of falling, in which the complete internal reflection occurs, is called the limit angle of complete internal reflection. With mirror reflection, the reflection angle is equal to the angle of fall. Surface, evenly in all directions, the lighting light falling on it is called absolutely matte.

51. Thin lenses. Lens - Detail of an optically transparent homogeneous material bounded by two polished refracting rotation surfaces. If the thickness of the lenses itself is small compared to the radii of curvature of spherical surfaces, then the lens is called thin. Lenses are there gathering and scattering. Gathering lens in the middle thicker than the edges, scattering lens, on the contrary, in the middle side thinner in the case of thin lenses it can be assumed that the main optical axis intersects with the lens at one point, which is called Optical Center for Lenses O. All direct passing through optical center called by-optical axes. If on the lens to send a beam of the rays parallel to the main optical axis, then after passing through the lens, the rays will be gather at one point F, which is called main focuslenses. The thin lens has two main focus, symmetrically located relative to the lens on the main optical axis. In collecting lenses, the tricks are valid, imaginary. Property lenses ability to give images of objects. Optical force measurement unit 1 diopter. Thin lenses have a number of shortcomings that do not allow to receive high-quality images.

One of the main concepts in electricity is an electrostatic field. Its important property is considered to work on the movement of charge in electric fieldwhich is created by a distributed charge that does not vary in time.

Terms of performance

The force in the electrostatic field moves the charge from one place to another. It does not completely affect the form of the trajectory. Determining the power depends only on the position of the points at the beginning and end, as well as, on the total size of the charge.

Based on this, you can draw the following conclusion: if the trajectory when moving the electric facility is closed, then all the work of forces in the electrostatic field has a zero value. At the same time, the form of the trajectory does not matter because the Coulomb forces produce the same work. When the direction in which the electric pressure moves, changes to the opposite, then the force itself also changes its sign. Therefore, a closed trajectory, regardless of its form, determines all the work produced by Coulomb forces equal to zero.

If several point charges take part in the creation of the electrostatic field, their overall work will develop from the amount of work produced by the Coulomb fields of these charges. The overall work, regardless of the form of the trajectory, is determined exclusively by the location of the initial and endpoints.

The concept of potential charge energy

Peculiar to the electrostatic field, allows you to determine the potential energy of any charge. In addition, it is more accurately installed work on the movement of charge in the electric field. To get this value, in space you need to select a specific point and potential charge energy located at this point.

The charge placed anywhere has potential energy, equal workperformed by the electrostatic field during the movement of the charge from one point to another.

IN physical sense, potential energy It is a value for each of the two different points of space. At the same time, the work on the movement of the charge is regardless of the paths of its movement and the selected point. The potential of the electrostatic field in this spatial point is equal to the work performed electrical forcesWhen a single positive charge is removed from this point into an infinite space.

Electrical field work

8.6. Work in the electrostatic field

Consider a homogeneous electric field. It is formed between charged planes, if they are parallel and infinitely large. Practically can be considered a homogeneous electric field between finite parallel charged planes, if the dimensions of them are significantly larger than the distanced. Between them. Consider moving a positive charge fieldq. In three cases. Let the field move this charge from the point A to the point A’ (Fig. 8.3). Field work in this case

If the field moves the charge from the pointb to point A 'then work

We now calculate the field work with the movement of an electric charge from point from to point A’ . Threaten the curves 3. For a large number of sections, each of which can be taken with great accuracy for the straight. Let such sites ben. Then

Since the field is homogeneous, the force remains constant for all sites.

Fig. 8.3.

From the above examples, it can be concluded that the operation of the electrostatic field does not depend on the way: it is the same for three cases, although the trajectory of the electrical charge is different.

Let the electrical field are formed by a point charge Q. We calculate the work of the forces of the field performed when moving along the power line of the chargeq 0. From point 1, located at a distancer 1. from the source of the field, to point 2 at a distancer 2. from it (Fig. 8.4). Workd. And on the movement of charge on an infinitely small pathdR Determined D A \u003d FDR. Since f \u003d q 0 e, then

Fig. 8.4.

For spot charge back

Then all work on the movement of chargeq 0. from point 1 to point 2 will be

Values designated φ 1 and φ 2 and naz field potentials of points 1 and 2, respectively. Hence,

Work on the movement of charge in the electrostatic field is equal to the product of the charge on the potential difference between the initial and endpoints. From here it is also seen that this work does not depend onforms of the way. If from

Therefore, the potential is a physical value, is numerically equal to the work that the electric field performs with the movement of a single positive charge from a certain point of the field into infinity. Or the potential of a certain point of the field is the value, is numerically equal to the work that the external force should perform by moving a single positive charge from infinity to this point. The potential of this point of the field determines the potential energy of a single positive charge placed at this point. If each of the chargesq 1, q 2, ..., q n forms at a certain point the field with the potential according toφ 1, φ 2, ..., φ n , the potential of the field formed at this point by all charges is equal to the algebraic amount of field potentials created by each charge separately:

In practice, the potential of the earth is conditionally taken equal to zero. Therefore, the grounded conductor has zero potential. In theoretical calculations, it is more convenient to connect the zero potential with a point on infinity.

The unit of potential difference can be introduced using the formula

In the SI per unit of potential difference taken volts (1 V). This is the difference in potentials between such two points, the transfer of charge into one pendant between which is accompanied by the performance of work in 1 J:

In the SGSE system, the difference between the potential difference is taken between the potential difference between the two points, the transfer of charge into one absolute electrostatic unit of charge between which is accompanied by the performance of work in 1 ERG:

Insofar as

Often enjoy an incoming unit of work and energy, which is called electron-volt (eV). One electron-volt equal to workaccomplished when moving the charge, which is equal to the charge of the electron, between two points of the field with a potential difference in 1 V. Electron charge is 1.6∙ 10 -19 CL, then

We write the value of the operation of a homogeneous electric field to move the electrical chargeq for distance d From point with potentialΦ 1. to point with potentialφ 2. Then

from

The geometric location with the same potential is called the equipotential surface. It is clear that the work that the field performs the field to move the electric charge along the same surface of the surface is zero. Since the force acting on the side of the field on the charge is not zero, then the work on the movement of the charge can be zero only when the direction of force is perpendicular to the direction of movement. Considering that the direction of force on the charge coincides with the direction of the field strength vector, it is possible to conclude the perpendicularity of the line of tension to the ECIPOTENCIAL surfaces.

The electrostatic field can be depicted graphically with the help of power lines, but also with the help of ECPOTENCIAL surfaces. Around each system of charges, an infinite set of ekvіpotentzіal sterns are carried out. They are accepted so that the potential differences between any neighboring equipotential surfaces were the same.

Knowing the placement of power lines of the electrostatic field, it is possible to construct equipotential surfaces and, on the contrary, according to the known placement of the ECPOTENCIAL surfaces, it is possible to determine the placement of power lines at each point.

Since the operation of the electrostatic field to move the charge does not depend on the form of the path, but is determined only by the potentials of endpoints, it turns out that work on a closed contour (Fig. 8.5) in the electrostatic field (AAAVd A, A B in D A, DR D A) is zero.

Fig. 8.5.

Fields for which the work on a closed contour is zero, called potential.

For any charge that is in an electric field, power affects. In this regard, when charging the charge, a certain operation of the electric field occurs in the field. How to make the calculation of this work?

The operation of the electric field is to transfer electric charges along the conductor. It will be equal to the product, and the time spent on the work.

Applying the formula of the Ohm Law, we can get several different options for the formula for current counting:

A \u003d U˖i˖t \u003d I²R˖T \u003d (U² / R) ˖T.

In accordance with the law of conservation of energy, the operation of the electric field is equal to the change in the energy of a single circuit section, and therefore the energy secreted by the conductor will be equal to the current operation.

Express in the SI system:

[A] \u003d VT˖˖ \u003d T˖˖ \u003d J

1 kv˖ha \u003d 3600000 J.

Let's experience experience. Consider the movement of the charge in the field of the same name, which is formed by two parallel plates of plates A and B and charged multi-chain charges. In such a field, the power lines are perpendicular to these plates on the entire length, and when the plate A will be charged positively, then e will be directed from A to V.

Suppose that a positive charge q moved from point A to point B on an arbitrary path AB \u003d s.

Since the force that acts on the charge, which is in the field, will be equal to F \u003d QE, the work performed when charging the charge in the field according to the specified path is determined by the equality:

A \u003d fs cos α, or a \u003d qfs cos α.

But s cos α \u003d D, where D is a distance between the plates.

Hence the following: a \u003d qed.

Suppose, now the charge Q will move from A and B in essence ACB. The operation of the electric field, perfect on this path, is equal to the amount of work performed in the individual sections of it: AC \u003d S₁, CB \u003d S₂, i.e.

A \u003d qes₁ cos α₁ + qes₂ cos ₂₂

A \u003d QE (S₁ COS α₁ + S₂ COS α₂).

But S₁ cos α₁ + S₂ cos α₂ \u003d D, and therefore, in this case, A \u003d QED.

In addition, suppose the charge Q is moving from A to B along an arbitrary line curve. To calculate the work perfect on this curvilinear path, it is necessary to bundle the field between the plates A and in some quantities that will be so close to one another that the individual sections of the path s between these planes can be considered direct.

In this case, the operation of the electric field produced on each of these segments of the path will be equal to A₁ \u003d QED₁, where D₁ is a distance between two adjacent planes. And full work on the entire path D will be equal to the product QE and the amount of distance D₁, equal to d. Thus, and as a result of the curvilinear path, the perfect work will be equal to A \u003d QED.

Examples considered by us show that the operation of the electric field to move the charge from any point to another does not depend on the form of the movement path, and depends solely on the position of these points in the field.

In addition, we know that the work that is performed by the strength of gravity when the body moves along the inclined plane, having the length L, will be equal to the work that the body performs when falling from the height H, and the height of the inclined plane. It means that work or, in particular, work when moving the body in the field of gravity, also does not depend on the form of the path, but it depends only on the difference in the heights of the first and last path points.

So it is possible to prove that this important property may have not only homogeneous, and any electric field. The strength of gravity has a similar property.

The work of the electrostatic field by moving point charge From one point to another is determined by a linear integral:

A₁₂ \u003d ∫ L₁₂Q (EDL),

where L₁₂ is the trajectory of the charge, DL is infinitely small move along the trajectory. If the circuit is closed, then the symbol ∫ is used for the integral; In this case, it is assumed that the contour bypass direction is selected.

The work of electrostatic forces does not depend on the form of the path, but only from the coordinates of the first and last movement points. Consequently, the forces of the field are conservative, and the field itself is potentially. It is worth noting that the work of any closed path will be equal to zero.

Potential. Potential difference. Voltage.
Potential electrostatic field - scalar valueequal to the ratio of the potential energy of charge in the field to this charge: - energy characteristic Fields at this point. The potential does not depend on the size of the charge placed in this field.
Because Potential energy depends on the choice of the coordinate system, the potential is determined up to constant. The potential reference point is chosen depending on the problem: a) the potential of the Earth, b) the potential of an infinitely remote point of the field, c) the potential of the negative condenser plate.
- The consequence of the principle of superposition of fields (the potentials are developing algebraically).
The potential is numerically equal to the operation of the field to move a single positive charge from this point of the electric field to infinity. In the C potential is measured in Volta:
Potential difference
Voltage - The difference of potential values \u200b\u200bin the initial and end-screen trajectories. Voltage Numerically equal to the operation of the electrostatic field when moving a single positive charge along the power lines of this field. The potential difference (voltage) does not depend on the choice coordinate systems!
The difference unit of potentials The voltage is 1 V if, when moving a positive charge in 1 CL along the power lines, the field makes a job in 1 J.
Communication between tension and voltage .
Tension is equal to the rate of change of potential along the direction d.
From this ratio you can see:
Equipotential surfaces. EPP - surface of equal potential. EPP properties: - Work when moving the charge along the equipotential surface is not performed; - vector of tension is perpendicular to the EPP at each point.

2. Model of the structure of the atomic nucleus. Nuclear power. Communication energy. Nuclear reactions.
In 1932 After the opening of Proton and Neutron, scientists D.D. Ivanenko (USSR) and V. Heisenberg (Germany) was put forward proton-neutron model of the nucleus of the atom.

According to this model:
- the kernels of all chemical elements consist of nucleons: protons and neutrons
- the nucleus charge is due only by protons
- the number of protons in the nucleus is equal to the sequence number of the element
- The number of neutrons is equal to the difference between the mass number and number of protons (N \u003d A-Z)

Conditional designation of the core of the atom of the chemical element:

X - symbol of chemical element
A is a mass number that shows:
- Mass of the nucleus in the whole atomic units of mass (A.E.M.)
(1A.E.m. \u003d 1/12 mass of carbon atom)
- the number of nucleons in the kernel (a \u003d n + z), where n is the number of neutrons in the nucleus of the atom
Z - the charge number that shows:
- the charge of the nucleus in elementary electrical charges (e.e.z.)
(1E.F. \u003d Electron Charge \u003d 1.6 x 10 -19 CL)
- Number of protons
- the number of electrons in the atom
- Serial number in the Mendeleev Table
Nuclear power - graduation forces connecting protons and neutrons in the kernel.

Properties:

1. Discipers of about 10 -13 cm. Strong interactions correspond to attraction, with a decrease in distance - repulsion.

2. Only dependent on the presence of an electric charge (the property of the charge independence) the same force acts on the proton and the neutron.

3. Intelligence with a limited number of nucleons (saturation property).

4. Interactive: Quickly decrease, starting with R ≈ 2.2. 10 -15 m.

Energy that is necessary for the complete cleavage of the kernel into individual nucleons is called communication energy. Communication energy is very large. In the synthesis of 4 g of helium, the same amount of energy is distinguished as when combining two coal cars.

The mass of the nucleus is always less than the sum of the masses of the rest of the protons and neutrons, its components.
The difference between the mass of the kernel and the sum of the masses of protons and neutrons is called the mass defect.

Formula for calculating the energy of communication:

- Mass defect.

m P - the mass of the proton; M N is a neutron rest mass. M I - the mass of the nucleus of the atom.

In atomic physics, mass is conveniently expressed in atomic units of the mass:

1 AEM \u003d 1.67 · 10 -27 kg. Energy and mass communication coefficient (equal to 2): c 2 \u003d 931.5 MeV / A · E · m.

Nuclear reactions - transforming atomic nuclei caused by their interactions with different particles or each other.

Symbolic recording: A + A \u003d B + B. When writing nuclear reactions, the laws of preservation of charge and mass number (number of nucleons) are used.

Examples:

The energy yield of the nuclear reaction is the difference between the total binding energy of particles involved in the reaction and reaction products.

Reactions occurring with energy release, called. Exothermic, with an absorption - endothermic.