The problem of the balance of the point charge, the condition of the balance of the charge

Two point charges are fixed. The condition to make the introduced third point charge in equilibrium 1 is fixed to fix two positive charges q1 and q2 of the same kind, and the third point charge is introduced q3, to make q3 in equilibrium, it must be subjected to the equilibrium force, that is, the coulomb force of q1 and q2 to it must be equal in magnitude and opposite in direction so that q3 must be placed between q1 and q2 and make the three collinear.

Point charge: In physics, charged bodies that are much smaller in linearity than they are from each other are called point charges.

First of all, if they are balanced, they are balanced by force. In all of them, there is only the electric field force, so the electric field force is conserved.

According to the electric field force formula f=kq1q2 r*r (q1 and q2 are the charges of the two charges, r is the distance between the two charges, and k electrostatic constant) and then let the third charge charge be x, and the distance from q1 is r, which is brought into the calculation respectively, so that f13=f23 (i.e., k8*10-9 *x r*r=k2*10-9*x (x, x, r, r.

It should be noted that the electrical properties of Q3 must be different from those of Q1 and Q2 (because if they are the same, the charges on both sides will not be conserved).

At the same time, the charge of Q3 must be less than that of Q1 and Q2 (for the same reason as the previous cause).

Assuming that the power on the side (as if it is the left) is small, then the charge on the far right must be affected by the force of the middle and left charges, and the two forces are in opposite directions (otherwise the force is unbalanced), but because the Coulomb force is proportional to the electricity, the left power is small, the Coulomb force is small, and the distance on the left is still farther, so the Coulomb force is smaller, so the charge force of the left charge to the right must be less than the force of the middle charge to the right charge, so it will never be balanced, so only the amount of charge in the middle can be minimized.

This problem is often encountered in electricity, following the principle of two identical sandwiches, two negative sandwiches positive, and then balancing the system of equations according to the force.

When the charge in a charged system (which can be a live conductor) is stationary so that the electric field distribution does not change with time, we say that the charged system has reached an electrostatic equilibrium.

If we consider that the electric charge needs to move hotly, then we can put it another way: the state in which there is no electric charge in the conductor (including the surface) to move is called the electrostatic equilibrium state of the conductor The characteristic of a conductor is that there are a large number of free electrons in its body.

They can move under the action of an electric field, which changes the charge distribution; In turn, changes in the charge distribution affect the electric field distribution (the charge q on the inductive conductor in the front section is segregated to the left end).

The state in which there is no directional movement of electric charge in a conductor (including the surface) is called the electrostatic equilibrium state.

Conductors in electrostatic equilibrium have the following characteristics: open fiber codes.

1. Internal field strength.

Zero everywhere. 2. At this time, the conductor is an equipotential body, and the surface of the conductor is an equipotential surface.

3. The direction of the field strength near the conductor surface is perpendicular to the conductor surface.

4. The conductor charge is distributed on the surface of the conductor, and it is related to the degree of bending of the conductor surface, the more curved the surface, the denser the charge.

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Problem description: The charges at the three points are in equilibrium, the charges are q1, q2, q3, and the electrostatic force constant is k, please deduce the positional relationship between them r12, r23, r13?

Analysis: The problem is a good imitation, and even if there is no external force field, even the two will not be balanced. Only in extreme cases, they are located in the same hole sock cover straight line, and are of the same sex on both sides, different in the middle, but not stable balance!

1(-)r12...2(+)r23...3(-)

f12 = k*q1*q2/(r12^2)

f23 = k*q2*q3/(r23^2)

f12 = f23

q1/(r12^2) =q3/(r23^2)

r12 : r23 : r13 = q1 : q3 :(q1 + q3 )

Wake up to find that the conclusion at the beginning is wrong: this balance is a stable balance! And the analysis of the force is also wrong!

f12 = k*q1*q2/(r12^2)

f23 = k*q2*q3/(r23^2)

f13 = k*q1*q3/(r13^2)

Q1 equilibrium condition: f12 - f13 = 0

q2/(r12^2) =q3/(r13^2) .1)

Q2 equilibrium condition: f12 - f23 = 0

q1/(r12^2) =q3/(r23^2) .2)

Q3 equilibrium condition: f23 - f13 = 0

q2/(r23^2) =q1/(r13^2) .3)

It can be obtained by any two of the three formulas.

q1*r23^2 = q2*r13^2 = q3*r12^2 = c...Give a constant that is easy to calculate.

So R12 = C Q3), R23 = C Q1), R13 = C Q2).

r12 : r23 : r13 = 1 q3 : 1 q1 : 1 q2

Three-point collinear: The three point charges must be in the same straight line.

If any one of them deviates from the straight line, then the other two will be subject to the gravitational or repulsive force that deflects upwards or downwards from that point charge and cannot be balanced (regardless of the point charge gravity).

Two identical differences: the same charge cannot be adjacent.

If the charge is ++- for the analysis of the positive charge in the middle, it is impossible to achieve equilibrium at all The two clamps are small: the amount of charge of the dissimilar charge in the middle should be the smallest.

If the amount of charge in the middle is larger, then the charge on one side will receive a larger gravitational force, but the repulsive force given by the other half will be smaller due to the small amount of charge and the distance is smaller, and it will not be able to achieve equilibrium at all.

Near, small, far, large: the middle charge is close to the one with the smaller charge on both sides, because the charge is small and the distance is close, so it can be balanced with the two gravitational forces with a large charge and a long distance, and the above laws are summarized by doing the problem.

How to solve the charge balance problem of three points in space? A mantra to help you get it done quickly.

I remember the teacher talked about a work equation: charge 12 and r3, charge 23 and r1, charge 13 and r2

Summary. I once tried a uniform electric field without a point charge in the laboratory, and it turned out that the distribution of the electric field was uniform, and there were no obvious electric field lines. SolutionYes, a uniform electric field without a point charge exists.

Since there is no point charge, the distribution of the electric field is uniform, there are no obvious electric field lines, but the intensity of the electric field is consistent, and the presence of the electric field can be determined by measuring the electric field strength. Extension: In addition, the uniform electric field without a point charge can also be explained by the electromagnetic field theory, that is, the electric field and the magnetic field in the electromagnetic field are independent of each other and can cancel each other out, thus forming a uniform electric field without a point charge.

I once tried a uniform electric field without a point charge in the laboratory, and it turned out that the distribution of the electric field was uniform and there were no obvious electric field lines. SolutionYes, a uniform electric field without a point charge exists. Since there is no point charge, the distribution of the electric field is uniform, there are no obvious electric field lines, but the strength of the electric field is consistent, and the presence of the electric field can be determined by measuring the intensity of the electric coarse field.

Extension: In addition, the homogeneous source strong electric field without point charge can also be explained by electromagnetic field theory, that is, the electric field and magnetic field in the electromagnetic field are independent of each other and can cancel each other out, thus forming a uniform electric field without point charge.

Excuse me, but please go into more detail?

Yes, an electric field without a point charge can also exist. For example, in an old Biheyun strong electric field, the electric field strength is the same, and an electric field without a point charge can also exist. In addition, there are some other electric fields, such as electromagnetic fields, which can also exist in the absence of a point charge.