Electric field is a special substance existing in the space around electric charge and changing magnetic field.This kind of material is different from the ordinary physical objects. Although it is not composed of molecular atoms, it isobjective existenceIt is a special substance with the objective properties of force and energy that ordinary substances possess.[1]
The force of electric field is characterized by: electric field hasForce, this force is calledElectric field force。The nature of the energy of the electric field is that when the charge moves in the electric field, the electric field force does work on the charge, indicating that the electric field has energy.[1]
In the 1830s, Faraday, an English scientist, put forward the idea that "there is an electric field generated by the electric charge". Later, physical theories and experiments not only confirmed Faraday's idea, but also proved that the electric field is an objective form of matter.The electric field is invisible and untouchable, in order to visually describe the points in the electric fieldelectric field intensityFaraday also introducedElectric field lineThe concept of.[8]
Charged bodySpecial substances around.The basic property of the electric field is to exert a powerful effect on the electric charge put into it.The interaction between charges is always carried out through an electric field.[4]
Differentiate and analyze two different electric fields:Coulomb electric fieldandInduced electric fieldCoulomb electric field is the electric field excited by the electric charge according to the Coulomb law, such aselectrostatic fieldIt is determined by the static electric chargeCoulomb's lawWhat is excited belongs to coulomb electric field, which can be found around various charged bodies.[5]
Induced electric fieldIt is excited by the changing magnetic field, pressMaxwell theoryThe changing magnetic field excites an electric field around it.for exampleBar magnetWhen the coil is inserted, the moving magnet changes the surrounding magnetic field, thus producingEddy electric field, vortex electric field generatesInduced electromotive forceThis electric field is the induced electric field[5]。
The electric field generated by static charge in its surrounding space is called electrostatic field;The electric field excited by the time-varying magnetic field in its surrounding space is calledInduced electric field。The electric field in general is the sum of electrostatic field and induced electric field.The electric field is aVector field, its direction is the force direction of the positive charge.[1]
Basic properties
one
Any charged body put into the electric field will be subject toElectric field forceRole of.[6]
two
Electric field can generate conductors put into electric fieldElectrostatic inductionPhenomenon.[6]
electrostatic field
An electrostatic field is an electric field excited by a static charge.This static charge is calledField source charge, referred to as source charge.The electric field line of electrostatic field starts from positive charge or infinity and ends at infinity ornegative charge。The electric field line direction of the electrostatic field is closely related to the field source charge.When the field source charge is positive, the electric field line of the electric field is divergent;When the field source charge is negative, the electric field line of the electric field is convergent.The work done by the electric field force moving charge is independent of the path.usePotential differenceDescribe the nature of the energy of the electric field, or useEquipotential surfaceVisually illustrate the distribution of electric field potential.[7]
The electric field excited by the changing magnetic field is calledInduced electric fieldorEddy electric field。Maxwell proposed that "the changing magnetic field will excite an electric field in the space around it, and it is this electric field that makesClosed loopProduced inInduced electromotive forceandInduced current”This electric field is calledEddy electric field。The electric field line of induced electric field is closed, without starting point and ending point.A closed electric field line surrounds a changing magnetic field.[7]
Describe electric field
Announce
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electric field intensity
A charge q at a certain position in the electric field, and its electric force F at that point is equal toCharge quantityThe ratio of Q is calledelectric field intensity, referred to as field strength.[6]
The electric field strength of each point in the electric field is independent of whether the charge is put in.[6]
In the same space, if several static charges generate electric fields in the space at the same time, the field strength at a point in the space is the sum of the field strength vectors generated at that point when the field source charges exist alone.[6]
Point chargeThe field strength formula of point charge Q at a point in vacuum is:
；Q is the size of the field source charge that generates the electric field.R is the distance from the studied point to the field source charge.[6]
The definition of electric field strength is based on the electric fieldForceCharacteristics.Charge excitedelectrostatic fieldAnd variable magnetic fieldEddy electric fieldAll apply.The characteristic of electric field is that it exerts an electric force on the chargeElectric field directionSame,negative chargeThe force direction is opposite to the electric field direction.Electric field is a kind of material with energy. Where the electric field is strong, the energy of the electric field is large.[7]
The force of electric field on electric charge can be determined when the electric field strength is known,dielectric(insulator）OfElectric breakdownIt is related to the field strength.[7]
The electric field strength of the point charge is determined by the point charge, andTentative chargeirrelevant.[7]
Electric field line
Electric field lineIt is a false curve drawn to visually depict the distribution of electric field.ThetangentThe direction is the field strength direction of the point.The density of these curves indicates the size of the field strength in this area. The field is strong where the electric field lines are dense, and vice versa.[6]
Characteristics of electric field line:[4]
one
The tangent direction of a point is the direction of the electric field intensity at that point.[4]
two
The density of electric field lines indicates the strength of electric field.[4]
three
The electric field lines of the electrostatic field are neither closed nor intersected, starting from the positive charge (infinity) and ending at the negative charge (infinity).[4]
four
The electric field line is perpendicular to the equipotential surface and along the direction of the electric field linepotentialLower.[4]
Understand and master the electric field line distribution of the electric field formed by positive point charges, negative point charges, two equal amounts of the same charge, and two equal amounts of different charges.[4]
Electric field line is not the track of electric charge movement, nor is itobjective existenceLine.Under special conditions,charged particleOfpath of particleIt can coincide with the electric field line.These special conditions are:[4]
one
The electric field line is a straight line;[4]
two
The initial velocity of charged particles is zero or the direction of initial velocity is on the same line with the direction of electric field line;[4]
three
Charged particles are only affected by electric force.[4]
The above three points must be met at the same time.[4]
Superposition of electric field
The electric field is a vector, if there are severalCharged bodyCoexistence, then their electric fields are superposed, that is, Ep=E1+E2, followingParallelogram rule。[4]
Electric field force F: the force that the electric charge receives in the electric field.[4]
Size F=Eq.[4]
Direction: the direction of positive charge receiving electric field force is the same as E, and the direction of negative charge receiving electric field force is opposite to E.[4]
Skills for judging the magnitude and direction of electric field strength
① Judging by the density of electric field lines, the denser the electric field lines are, the greater the field strength is, the thinner the electric field lines are, and the smaller the field strength is.
② According to equivalencyEquipotential surfaceThe density of is used to determine the field strength. The field strength is strong in the dense area of isochromatic equipotential surface and small in the sparse area.
(2) Judgment skill of electric field intensity direction
① The direction of the electric field force on a positive charge at a point, that is, the direction of the electric field intensity at that point
② The direction of electric field intensity is on the same line as the tangent line of electric field line and points to the direction of potential reduction.
③ The direction of electric field intensity is perpendicular to the equipotential surface and points to the direction of potential reduction.
Knowing the electric field line of an electric field, you can determine the direction and size of the field strength, draw an equipotential surface, and determine the level of the potential (the potential decreases along the direction of the electric field line).[7]
It should be noted that the electric field line is not chargedpath of particle。The force direction andaccelerationDirection, it is impossible to determine the speed direction and motion track of the charge.When the electric field line is a straight line, the acceleration of charge movement is parallel to the electric field line, and the trajectory of charge movement coincides with the electric field line.[7]
Electric field force
one
Definition: The interaction between charges occurs through an electric field.As long as there is a charge, there is an electric field around the charge. The basic property of the electric field is that it affects thechargeThe force is called electric field force.[7]
two
Direction:positive chargeAlong the tangent direction of the electric field line,negative chargeThe opposite direction along the tangent direction of the electric field line.[7]
three
Calculation: The calculation formula of electric field force is F=qE, where q is the charge amount of the point charge, E is the field strength or W=Fd, or it can be calculated according to the distance between the work done by the electric field force and the movement in the direction of the electric field force.electromagneticsAnother important formula in the formula W=qU (where U is the potential difference between two points) is derived from this formula.[7]
four
Functions of electric field force:[7]Due to the extensive effect of electric field force, it is applied to particlesacceleratorNavigation correction in aerospace industry.yesNew substancesThe processing of and changes in the arrangement of substances may be one of the main driving forces in the future, and so on.[7]
five
Electric field forceResearch direction of[7]In the future, the aerospace industry will be greatly developed in the presence of electric force, such as the use of electric field protective layer (which can make aircraft lighter);And letAerocraftFlight relying on electric field (instead of existing engine);Electric field atNuclear matterThe decay ofenergy）。[7]
