What does the electromagnetic formula F = QE mean?

F: Coulomb force
q: Quantity of charge
E: Electric field intensity

How to understand the two expressions of electric field strength e = f / Q e = q / r2?

The basic characteristic of the electric field is that it can make the charge in the electric field subject to the force. The electric field strength e of a certain point in the electric field is defined as the ratio of F and Q of the static test charge placed at the point, i.e. e = f / Q

Coulomb's law formula

Coulomb's law can be written as F = (kq1 / R power) * Q2 or F = (KQ2 / R power) * Q1
Kq1 / R is the electric field excited by Q1 at R, KQ2 / R is the electric field excited by Q2 at R
F=Eq

On the formula of Coulomb's law
Coulomb's law can be written as F = (kq1 / R power) * Q2 or F = (KQ2 / R power) * Q1
What do (kq1 / R) and (KQ2 / R) denote

Kq1 / R is the electric field excited by Q1 at R, KQ2 / R is the electric field excited by Q2 at R
F=Eq

What is Q in the field strength formula e = KQ / r2
What is the relationship between Q 1 and Q 2 in Coulomb's law f = kq1q2 / R2 and Q in the field strength formula e = f / Q. how is the formula e = KQ / r2 obtained?

E=F/q
F=KQ1Q2/R²
Will 2 generations 1
Elimination of correlation
E = KQ / R & sup2;
Where q is the charge at the center

Understanding of electric field strength formula e = KQ / r2
When R approaches 0, the field strength approaches infinity, which has no physical meaning. How to understand this?

In other words, any charge has a radius. Experiments show that elementary particles (including protons, neutrons, etc.) have a radius of charge

According to the field strength formula e = KQ / R2 of point charge, the field strength is inversely proportional to the square of the distance between the field source charge and the field source charge. Try to explore whether the field strength (combined field strength) of a point on the vertical line of the same amount of heterogeneous charge is inversely proportional to the square of the distance between the point and the positive (or negative) charge

Let R be the distance between two charges
The field strength of + Q on the left side is KQ / R & # 178;, the angle between the direction and the horizontal plane is θ, obliquely upward
The field strength of - Q on the right side is KQ / R & # 178;, the angle between the direction and the horizontal plane is θ, inclined downward
It can be seen that the combined field strength is just offset in the vertical direction
E = 2 * (KQ / R & # 178;) cos θ
Because r changes and cos θ also changes, the field strength at a point is not inversely proportional to the square of the distance from the change point to the charge

Why is e = u / d only suitable for uniform electric field and E = KQ / r2 only suitable for electric field formed by point charge?

E = KQ / R2 is generated under the action of electrostatic force, so it is only for the position of the point. Moreover, the electric field strength changes with the increase of distance. It is troublesome to use e = u / d
E = u / D is derived from UQ = eqd, and it is convenient to calculate the equation when e is constant. In fact, it can also be used for point charge, but it is the average E

How to understand Coulomb's law

Introduction of Coulomb's law
Coulomb's law is one of the basic laws of electromagnetic field theory. The force between two static point charges in vacuum is directly proportional to the product of the two charges, and inversely proportional to the square of their distance. The direction of the force is along the line of the two point charges, and the same charges repel each other, The formula is: F = k * (Q1 * Q2) / R ^ 2 (when using the Coulomb's law to calculate, even if the negative charge is encountered, the absolute value of the charge quantity will be brought in for calculation, and the repulsion or gravitation will be judged according to the electricity after calculation)
The condition of Coulomb's Law: in vacuum, it must be a point charge
Note: this time does not necessarily require static, because in the usual questions and promotion, a large part does not consider whether the point charge is static
Verification of Coulomb's law
Coulomb's law was summed up by Coulomb's torsion scale experiment from 1784 to 1785. The structure of the new scale is as follows: a scale rod is suspended under a thin metal wire. There is a small ball a at one end and a balance P at the other end. Next to a is another fixed ball B of the same size as it. In order to study the force between charged bodies, a and B are first charged, At this time, the scale rod will deflect due to the force on the a-end. Turn the hanging button on the top of the hanging wire to make the ball return to its original position. At this time, the torsion moment of the hanging wire is equal to the torque of the electric power applied to the ball A. if the relationship between the torsion moment of the hanging wire and the torsion angle has been calibrated in advance, the angle reading of the pointer on the knob and the known length of the scale rod, We can know the force between a and B at this distance
How to compare the force
Coulomb's law formula
COULOMB’S LAW
Coulomb's law describing the interaction between charges at rest
In vacuum, the force of point charge Q1 on Q2 is 0
F=k*(q1*q2)/r^2
Among them:
R -- the distance between the two
R -- vector path from Q1 to Q2
K -- Coulomb constant
If Q1 and Q2 have the same sign, f 12Y is repulsive force along r direction;
If the two signs are different, then f 12 along - R direction - suction
It is obvious that the force of Q2 on Q1
F21 = -F12 （1-2）
In MKSA system of units
Unit of force F: Newton (n) = kg · M / S2 (dimension: MLT - 2)
Unit of electric quantity Q: Coulomb (c)
Definition: when the current flowing through a surface is 1 ampere, the current passing through it every second
1 Coulomb, i.e
1 Coulomb (c) = 1 ampere · second (a · s) (dimension: it)
Proportional constant k = 1 / 4pe0 (1-3) = 9.0x10 ^ 9N · m2 / Ku 2
E0 = 8.854 187 818 (71) × 10 - 12 Ku 2 / N · M 2 (usually expressed as farad / M)
Permittivity of vacuum
Explanation: it is also called absolute permittivity. The symbol is ε O. it is equal to 8.854187817 × 10-12 fa / m. It is an error free constant of the permeability and the velocity of light in vacuum
The physical meaning of Coulomb's law
(1) Only when the scale of the charged body is far less than the average distance between the two, it can be regarded as a point charge
(2) The Coulomb force needs to be modified to Lorentz force when there is relative motion between static charges. However, the practice shows that as long as the relative motion speed of charges is far less than the speed of light C, the result given by Coulomb's law is very close to the actual situation
[example 1-1] compare the Coulomb force and gravitational force of proton and electron in hydrogen atom (both are inverse distance square forces)
According to the classical theory, the radius of the "orbit" of the electron in the ground state hydrogen atom is 5.29 × 10 - 11 meters
The linearity of nucleus and electron is less than 10-15m, so they can be regarded as "point charge"
The electric quantity e ≈± 1.60 × 10-19 Coulomb mass MP ≈ 1.67 × 10-27 kg me ≈ 9.11 × 10-31 kg
The gravitational constant G ≈ 6.67 × 10-11 n · M 2 / kg 2
Coulomb force Fe = - E2R / 4pe0r3 and gravitational force FG = - gmpmer / R3
The ratio of Fe / FG = E2 / 4pe0gmpme ≈ 2.27 × 1039 (1-6)
It can be seen that the electromagnetic force plays a decisive role in the atomic and molecular structure, which is far greater than the force caused by universal gravitation, that is to say, the influence of mass on objects is far less than that of electromagnetic force, and the force between charges increases with the increase of charge amount, and decreases with the increase of distance
Notes on learning and applying Coulomb's law
(1) Coulomb's law is only applicable to the calculation of the interaction between two point charges, while Coulomb's law is not applicable to the interaction between non-point charges
(2) When Coulomb's law is applied to calculate the interaction force between point charges, the "+" and "-" symbols representing positive and negative charges need not be substituted into the formula. In the calculation process, the absolute value can be used to calculate, and the result can be used to determine the force as gravitational or repulsive force and the direction of the force according to the positive and negative charges
(3) The Coulomb force obeys Newton's third law. Don't think that the charge with large amount has great force on the charge with small amount

Who can explain Coulomb's law in detail? Thank you

The force between two static point charges in vacuum is directly proportional to the product of the charged quantity of the two charges and inversely proportional to the square of their distance. The direction of the force is along the line of the two point charges. The charges with the same name repel each other and the charges with different names attract each other. The formula is: F = k * (Q1 * Q2) / R ^ 2

What does the electromagnetic formula F = QE mean?