The electric field is one of the theoretical concepts explaining the phenomena of interaction between charged bodies. The substance cannot be touched, but one can prove existence, which was done in the course of hundreds of field experiments.
Interaction of charged bodies
They used to consider outdated theories as utopias, while the men of science are not stupid at all. Today Franklin’s teaching on electrical fluid, the prominent physicist Epinus, is ridiculous, devoted a whole treatise. Coulomb's law was discovered experimentally on the basis of torsional weights; Georg Om used similar methods in deriving the known equation for a chain segment. But what lies behind all this?
They must admit that the electric field is simply another theory, not inferior to a franklin liquid. Today there are two facts about substance:
- A constant electric field exists around a charged body. There are two signs of particles, objects can attract, repel. They are taught in school, it makes no sense to discuss the issue further here. The field strength indicates in which direction the force will act on a positively charged particle - therefore, it is a vector quantity. The body is surrounded by lines of equivalence, at each point of which the direction is unique. For a point charge diverge rays to the sides. The direction is determined by the sign: the vectors tend away from the positive.
- The electric field varies in time and space. According to Maxwell's equations, it generates a magnetic one, described by a similar law. The vectors of the fields lie in mutually perpendicular planes, they exist in a close relationship. Electromagnetic wave, commonly used in everyday life, technology for transmitting information through the air.
The stated facts laid the foundation for the modern understanding of interactions in nature, and are the backbone of the theory of close interaction. In addition to her scientists put forward other assumptions about the essence of the observed phenomenon. The theory of short-range action implies an instantaneous spread of power without the participation of the ether. Since phenomena are more difficult to touch than the electric field, many philosophers have called such views idealistic. In our country, they were successfully criticized by the Soviet authorities, because, as you know, the Bolsheviks did not like God, pecked at every opportunity the idea of the existence of something “dependent on our ideas and actions”( studying the super abilities of Juna).
Franklin explained the positive, negative charges of bodies with excess, insufficiency of electric fluid.
Characteristics of the electric field
The electric field is described by a vector quantity - intensity. An arrow whose direction coincides with the force acting at a point on a unit positive charge, the length is proportional to the modulus of the force. Physicists find it convenient to use the potential. The value is scalar; it is simpler to imagine the temperature as an example: at each point in space some value. Under the electric potential understand the work done to move a single charge from a point of zero potential to a given point.
The field described by the method indicated above is called irrotational. Sometimes referred to as potential. The function of the electric field potential is continuous, changing smoothly along the length of space. As a result, we select points of equal potential, folding surfaces. For a single charge, the sphere: further object, weaker field( Coulomb's law).Surfaces are called equipotential.
To understand the Maxwell equations, get the idea of several characteristics of a vector field:
- The gradient of the electric potential is called a vector, the direction coincides with the fastest growth of the field parameter. The value is greater, the faster the value changes. A gradient from a smaller potential value to a larger one is directed:
- The gradient is perpendicular to the equipotential surface.
- The greater the gradient, the closer the location of the equipotential surfaces that differ from each other by a given amount of potential of the electric field.
- The potential gradient, taken with the opposite sign, is the electric field strength.
- Divergence is a scalar value calculated for the electric field strength vector. It is an analogue of the gradient( for vectors), shows the rate of change of magnitude. The need for the introduction of additional characteristics: the vector field is devoid of a gradient. Consequently, a certain analogue is needed for the description - divergence. The parameter in the mathematical notation is similar to the gradient, denoted by the Greek letter nabla, is used for vector quantities.
- The rotor of a vector field is called a swirl. Physically, the value is zero with a uniform change in the parameter. If the rotor is non-zero, closed bends of lines appear. In potential fields of point charges, by definition, there is no vortex. Not necessarily the lines of tension in this case are straightforward. Just change smoothly, without forming a whirlwind. A field with a nonzero rotor is often called a solenoidal field. Often used synonym - vortex.
- The total flux of a vector is represented by the integral over the surface of the product of the electric field intensity over an elementary area. The limit of magnitude as the body's capacity tends to zero is the field divergence. The concept of the limit is studied by the senior classes of the secondary school, the student can make some idea for discussion.
Maxwell's equations describe a time-varying electric field and show that in such cases a wave occurs. It is considered to be one of the formulas indicates the absence in nature of isolated magnetic charges( poles).Sometimes in the literature we meet a special operator - the Laplacian. It is denoted as square nabla, calculated for vector quantities, represents the gradient of the field gradient.
Using these quantities, mathematicians and physicists calculate electric and magnetic fields. For example, it was proved: a scalar potential can only be at an irrotational field( point charges).Other axioms are invented. The rotor vortex field is devoid of divergence.
Such axioms are easily taken as the basis for describing the processes occurring in real existing devices. Antigravity, perpetual motion engine would be a good help to the economy. If no one succeeded in putting Einstein’s theory into practice, Nikola Tesla’s developments are explored by enthusiasts. Missing rotor, divergence.
A brief history of the development of the electric field
- The first milestone is the introduction of the notion of potential to science. The parameter in the theory of electricity characterizes the field strength. The great astronomer introduced potential in relation to celestial mechanics in 1773.
- In 1785 Coulomb using torsional weights empirically derived the law of interaction between electric charges.
- In 1812, Poisson associated the concept of potential with electrical and magnetic phenomena.
- In 1819, Oersted showed empirically: a magnetic needle can be deflected by a current flowing through a conductor( see. Magnetic induction), which creates a circular electric field of constant intensity around it.
- 1827 - Georg Om derived a law relating the magnitudes of voltage and current through the resistance of a section of a circuit. The effect of the field on the magnetic needle was used. The resultant force was measured using a torsion balance.
- In 1831, M. Faraday publishes works on electromagnetism, showing the interconnection of two heterogeneous fields, explains the practical side of the issue( electric motor).Faraday dealt with questions at that time for almost 10 years, he did not dare to publish the outline, stopped by criticism from his mentor Davy, who considered the idea of plagiarism( see Wikipedia).The views of the scientist found a hot response in the hearts of the materialists. According to M. Faraday, the field propagates at a finite velocity in the ether( the speed of light known from physics).
- The Lenz rule, derived in 1833, led to the discovery in 1838 of the reversibility of electric machines( from work to energy generation).
- In the second half of the XIX century, units of measurement of magnetic and electric fields were introduced( Tesla appeared in the second half of the XX century when the SI system of units was approved).
- In 1973, Maxwell, for the first time, expounded the theory in the Treatise on Electricity and Magnetism of the relationship of electric, magnetic fields, backed by equations.
The formulation of the theory was followed by numerous works on the application of electric and electromagnetic fields in practice, the most famous of which in Russia consider Popov's experience in transmitting information through the air. A number of questions arose. Maxwell’s slender theory is powerless to explain the phenomena observed during the passage of electromagnetic waves through ionized media. Planck suggested that radiant energy is emitted in metered portions, later called quanta. The diffraction of individual electrons, kindly demonstrated by Youtube in the English version, was discovered in 1949 by Soviet physicists. The particle simultaneously showed wave properties.
This tells us that the modern idea of a constant and alternating electric field is far from perfect. Many people know Einstein, they are powerless to explain what a physicist has discovered. The theory of relativity of 1915 binds electric, magnetic fields and bruising. True, the formulas in the form of a law were not presented. Today it is known: there are particles moving faster, light propagation. Another stone in the garden.
Systems of units have undergone a permanent change. The initially introduced GHS, based on Gaussian practices, is not convenient. The first letters denote base units: centimeter, gram, second. Electromagnetic quantities are added to the GHS in 1874 by Maxwell and Thomson. The USSR began to use the ISS in 1948( meter, kilogram, second).The end to the battles was laid in the 1960s by introducing the SI system( GOST 9867), where the electric field strength is measured in V / m.
Using the electric field
The accumulation of electric charge occurs in capacitors. Consequently, a field is formed between the plates. Since the capacitance directly depends on the magnitude of the intensity vector, in order to increase the parameter, the space is filled with a dielectric.
Indirectly, electric fields are used by kinescopes, Chizhevsky chandeliers, the grid potential controls the movement of the rays of electron tubes. Despite the lack of a coherent theory, electric field effects underlie many images.