\u003e\u003e Physics 10 class \u003e\u003e Physics: communication between tension electrostatic field and the difference in potentials. Equipotential surfaces
Each point electric field Corresponding certain values \u200b\u200bof potential and tension. Find the connection of the electric field strength with the potential.
Let the charge q. Moves in the direction of the intensity vector of a homogeneous electric field from the point 1
exactly 2
farm 1
(fig.14.28.). Electrical field makes a job:
This work according to formula (14.19) can be expressed through the potential difference at points 1
and 2
:
Equating expressions for work, we will find the field strength vector module:
In this formula U. - the difference of potentials between points 1
and 2
which are associated with a movement vector coinciding in the direction of tension (see fig.14.28.).
Formula (14.21) shows: the less the potential changes at a distance, the smaller the tension of the electrostatic field. If the potential does not change at all, the field strength is zero.
Since when moving a positive charge in the direction of tension vector, the electrostatic field makes positive operation, the potential is more potential.
Hence, the electric field strength is directed toward the decrease in the potential.
Any electrostatic field in a sufficiently small area of \u200b\u200bspace can be considered homogeneous. Therefore, formula (14.21) is valid for an arbitrary electrostatic field, unless the distance is so small that changes in the field strength at this distance can be neglected.
Unit of electric field strength. The electrical field strength unit in C is installed using formula (14.21). The electric field strength is numerically equal to one if the potential difference between two points at a distance1m in a homogeneous field is equal 1 V. The name of this unit is volts per meter (in / m).
Tensions can also be expressed in Newton to pendant. Really,
Surfaces of equal potential called equipotential.
Equipotential surfaces uniform field represent planes ( fig.14.29.), and fields point charge - concentric spheres ( fig.14.30).
Like the power lines, the equipotential surfaces qualitatively characterize the field distribution in space. The vector of tension is perpendicular to the equipotential surfaces and is directed towards a decrease in the potential.
Equipotential surfaces are usually built so that the potential difference between two adjacent surfaces is constant. Therefore, according to formula (14.21), the distance between adjacent equipotential surfaces increases with the removal from the point charge, since the field strength decreases.
Equipotential surfaces of a homogeneous field are located at equal distances from each other.
Equipotential is the surface of any conductor in the electrostatic field. After all, the power lines perpendicular to the surface of the conductor. And not only the surface, but all points inside the conductor have the same potential. The field strength inside the conductor is zero, it means that zero and the potential difference between any dots of the conductor.
The electrostatic field strength module is numerically equal to the difference in potentials between two close points in this field divided by the distance between these points.
???
1. What is the difference in the potentials between the two points of the charged conductor?
2. How is the potential difference with the electric field strength?
G. Y. Mikishev, B.B. Bukhovtsev, N.N.Sotsky, Physics 10
Potential The electrostatic field is a scalar value equal to the ratio of the potential energy of charge in the field to this charge:
Energy characteristics of the field 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 with an accuracy of constant.
The consequence of the principle of superposition of fields (the potentials are developing algebraically).
Potential numerical equal to work Fields to move 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 point of the trajectory.
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
tension is equal to the potential gradient (potential change rate along the direction d).
From this ratio you can see:
1. The vector of tension is directed towards the reduction of the potential.
2. The electric field exists if there is a potential difference.
3. Unit of tension: - Field tension is equal
Log in magnetic induction. Gauss theorem for magnetic field.
The flow of the magnetic induction vector (magnetic flow) through the DS site is called Scalar physical value equal
Magnetic Induction Vector Stream F. in through an arbitrary surface s is equal 
The Gaussian Theorem for the Field in: The stream of the magnetic induction vector through any closed surface is zero:
full magnetic stream adopted with all solenoid twists and called streaming,
Conductors in the electrostatic field. Electrical capacity of a secluded conductor.
If you put the conductor into an external electrostatic field or charge it, then an electrostatic field will act on the conductor charges, as a result of which they will begin to move. The movement of charges (current) continues until the equilibrium distribution of charges is established, at which the electrostatic field inside the conductor addresses to zero. This happens for a very short time. In fact, if the field was not zero, then in the conductor there would be an ordered movement of charges without energy costs from an external source, which contradicts the law of energy conservation. So, the field strength at all points inside the conductor is zero:
In Gaussu 
Magnitude
call electrical capacity (or simply capacity) of a secluded conductor. The capacity of the secluded conductor is determined by the charge, the message of which the conductor changes its potential per unit.
The capacitance of the conductor depends on its size and shape, but does not depend on the material, the aggregate state, the shape and size of the cavities inside the conductor. This is due to the fact that excess charges are distributed on the external surface of the conductor. The capacity is also not dependent on the charge of the conductor or on its potential. This does not contradict the formula, since it only shows that the capacity of the secluded conductor is directly proportional to its charge and inversely proportional to the potential.
Electricity unit - Farad(F): 1F
| 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 CB)
- 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 availability electric charge (Charging Independence Property) The same force acts on a proton and 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.
What two characteristics of the electrostatic field do you already know? How are they defined?
Why do the electric field depict the power lines?
Each point of the electric field corresponds to certain values \u200b\u200bof potential and tension. Find the connection of the voltage of the electric field with the difference in potentials.
Let the charge q move in the direction of the voltage vector of the homogeneous electric field e from point 1 to point 2, located at a distance Δd from point 1 (Fig. 14.33). Electrical field makes work
This work according to formula (14.19) can be expressed through the potential difference between points 1 and 2:
A \u003d g (φ 1 - φ 2) \u003d -qδφ \u003d qu. (14.20)
Equating expressions for work, find the field of field strength vector module:
In this formula, U is the potential difference between points 1 and 2, lying on the same power line (see Fig. 14.33).
Formula (14.21) shows: the less the potential changes at a distance Δd, the less the tension of the electrostatic field. If the potential does not change at all, the field strength is zero.
Since when moving a positive charge in the direction of tension vector, the electrostatic field makes positive operation
A \u003d q (φ 1 - φ 2)\u003e 0,
the potential φ 1 is greater than the potential φ 2.
Any electrostatic field in a sufficiently small area of \u200b\u200bspace can be considered homogeneous.
Formula (14.21) is valid for an arbitrary electrostatic field, unless the distance ΔD is so small that changes in the field voltage at this distance can be neglected.
Unit of electric field strength. The unit of tension of the electric field in C is installed using formula (14.21).
Voltage unit - volt on meter (In / m).
The tension, as we already know, can also be expressed in Newton to pendant. Really,
Equipotential surfaces. When charging the charge at an angle of 90 ° to the power lines, the electric field does not work, since the electrostatic force is perpendicular to the movement. So, if the surface perpendicular to the power lines perpendicular at each point, then when the charge is moving along this surface, the work is not performed. And this means that all points of the surface, perpendicular to the power lines, have the same potential.
The equipotential surfaces of a homogeneous field are planes (Fig. 14.34, a), and the fields of point charge are concentric spheres (Fig. 14.34, b).
Equipotential surfaces qualitatively characterize the field distribution in space is similar to how the level lines reflect the surface relief on geographic maps. The voltage vector is perpendicular to the equipotential surfaces and is directed towards a decrease in the potential.
Equipotential surfaces are usually built so that the potential difference between two adjacent surfaces is constant. Therefore, according to formula (14.21), the distance between adjacent equipotential surfaces increases with removal from a point charge, since the field strength decreases.
Equipotential surfaces of a homogeneous field are located at equal distances from each other.
Questions to paragraph
1. What is the difference in the potentials between the two points of the charged conductor?
2. How is the potential difference with the tension of the electric field?
3. The potential of the electrostatic field increases in the bottom upward direction. Where is the field strength vector?
4. How are equipotential surfaces are built?
5. As in the picture of the equipotential surfaces of the field, can be judged by the value of tension at different points?
The potential is an important characteristic of the electric field, it determines all sorts of energy characteristics of the processes passing in the electric field. In addition, the calculation of the field potential is easier to calculate tension, if only because it is a scalar (and not vector) value. Of course, the potential and tension of the field are hung with itself, now we will establish this connection. Let in an arbitrary electrostatic field point charge q. Made a small move Δr. From the point 1 exactly 2 (Fig. 259).
Neglecting the field strength E. In this area, work, perfect field can be written in the form
By definition, this value is equal to the difference in potentials taken with the opposite sign divided by the amount of charge, therefore
38) Energy of the energy field. Pottsyl. Pottzal Point Dot Charge
Energy of electromagnetic field - energy, Prisoner B. electromagnetic field. [ the source is not specified 452 days ] This also includes private cases of pure electric And clean magnetic field.
The concept of the operation of the electric field to move the charge is in full compliance with the definition of mechanical work:
where - the potential difference (the term voltage is also used).
In many tasks, there is a continuous transfer of charge for some time between points with a given potential difference, in which case the formula for work should be rewritten as follows:
where is the current of the current.
Potential (from lat. Potentia is strength), in a broad sense - means, reserves, sources available and can be mobilized, are powered, used to achieve a certain goal, implementation of the plan, solving any task; Opportunities individuals, societies, states in a certain area: Economic P. (see Economic potential), production P. On the application of the term "P." in mathematics, physics, technology, biology and chemistry, see delaying potential, potential, , Damage potential, chemical potential, electromagnetic field potentials, etc. Potential, matemat. and Piz. , Expression in higher mathematics, having important use in the study of electrical and magnetic phenomena, denoting the voltage of electricity and magnetism on the surface of the conductors and serving to measure the current ("potential difference"). Potential "L, a, m. [From Latin. Potentia is strength, the possibility]. 1. A physical concept characterizing the magnitude of potential energy at a specific point of space (Piz., Tech.). P. Power of attraction. Potential differences. 2. Inend. A set of funds, the conditions necessary for keeping, maintaining, preserving something. (New. Polit.). P. Wars (refressures for warfare). There is now a more relevant and noble task for both large and small countries than landing the organization, strengthening and inviolability of the entire potential of the world.
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Potential. Potential difference. Voltage. | |
|
Potential The electrostatic field is a scalar value equal to the ratio of the potential energy of charge in the field to this charge: Energy characteristics of the field 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 | |
|
|
39) Permanent current. EMF. Ohm laws in integral and differential forms
D.C, (english direct. current) - electricitywho is over of time Does not vary in size and direction.
In the figure on the right red graphic depicted direct current. Along the horizontal axis, the scale of time is postponed, and vertical - scale tok. or electric voltage . As can be seen, the DC graph is straight line, parallel horizontal axis (time axis).
DC value and electrical tension for any point of time persists unchanged.
With constant current through each cross section explorer per unit time flows the same amount electricity (electrical charges).
Electromotive force (EMF) is a scalar physical value that characterizes the work of third-party forces, that is, any silnerelectric origin acting in quasi-stationary circuits of permanent or alternating current. In the closed conductive circuit, EDC is equal to the work of these forces to move a single positive charge along the entire contour.
By analogy with the tension of the electric field, the concept is introduced strength of third-party power Under which you understand the vector physical value equal to the ratio of a third-party strength acting on a test electric charge, to the magnitude of this charge. Then in the closed circuit of EMF will be equal to:
where is the contour element.
Ohm's law In the integral form, the Ohm law for the electrical circuit site is: U \u003d Ri where: U is the voltage or potential difference, I is the current strength, R - resistance. Ohm law also applies to the entire chain, but in a somewhat modified form: i \u003d E / (R + R), where: E - EDC chains, I is the current of the current in the chain, R is the resistance of all elements of the chain, R - the internal resistance of the source Nutrition. Ohm's law in differential form resistance R depends on both the material by which the current flows and on the geometric size of the conductor. It is useful to rewrite the Ohm law in the so-called differential form, in which the dependence on geometric dimensions disappears, and then the OMA's law describes the exclusively electrically conductive properties of the material. For isotropic materials, we have: j \u003d σ * e where J is a current density vector, σ is a specific conductivity, E is the voltage vector of the electric field. All values \u200b\u200bincluded in this equation are the functions of coordinates and, in general, time. If the material is anisotropine, the direction of current and voltage density vectors may not coincide. In this case, the specific conductivity is a tensor of rank (1, 1). The section of physics studying the flow of electric current in various media is called electrodynamics of solid media
40.Con Joule - Lenza law - quantity of heat Q.excreted per unit time on the plot of electric. chains with resistance R. When the post is going on. Tok. I.well Q \u003d RI. 2
41. Work and current power. When current flows over a homogeneous section of the chain, the electric field makes a job. During the Δt according to the chain, the charge Δq \u003d i Δt proceeds. The electric field on the highlighted hassle makes the work
CPD current source.
42. Magnetic field. Law of Bio-Savar Laplas. Law Bio Savara Laplas - Magnetic field of any current can be calculated as vector sums of fields created by separate sections of currents.
A magnetic field - Power fieldacting on moving electric charges and on the bodies possessing magnetic Moment, regardless of their state movement, Magnetic component electromagnetic field .
Magnetic field can be created current charged particles and / or magnetic moments electrons in atoms (and the magnetic moments of others particles, although it is noticeably less) ( permanent magnets).
