Why is the potential of each point in the electric field formed by a positive charge positive

The electric potential is relative, the magnitude of the electric potential at a certain point is relative to the zero electric potential, the selection position of the zero potential is different, the electric potential of the point is different, the selection of zero electric potential is arbitrary, usually the ground or infinity is selected as the zero electric potential point. (If you specify that infinity is a point of zero potential, because the electric field lines of the positive charge can point to infinity, and because the electric potential gradually decreases along the electric field lines, the electric potential of each point in the electric field formed by the positive charge is zero) The case you are talking about is only true when the zero potential surface is infinite.

1. The electric field lines of the positive charge start from the positive charge and end at infinity.

2. The electric potential decreases along the direction of the electric field line.

3. The electric potential at infinity is zero.

The direction of the electric field is from the positive charge to the negative charge.

People define the space without charge, the electric potential as 0

Then if there is a positive charge and a negative charge placed on each side of this place far away.

The potential of the positive charge to the negative charge is gradually decreasing.

The closer it is to the positive charge, the greater the potential is greater than 0.

I hope you can understand this explanation, and don't get too sharp.

Because it is usually specified that the infinity electric potential is 0

From positive charge to infinity, the electric potential gradually decreases.

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Analysis: To understand electric potential energy, to understand its concept, the reason for having electric potential energy is that the electric field force has the ability to do work.

All potential energy, remember a sentence, the electric field force is doing work, the electric potential energy is decreasing, the electric field force is negative doing work, the electric potential energy increases, you can think about the gravitational potential energy if you can't think of it; It can be understood in this way that in the process of doing positive work, the electric potential energy converts energy into other forms of energy through the form of work, so the electric potential energy decreases.

The electric potential energy at infinity is 0 because the charged object at infinity is not affected by the electric field force, so the electric field force does not have the ability to do work.

Move a positive charge from infinity to a certain position of the positive charge electric field, the direction of the electric field force is opposite to the direction of displacement, the electric field force is negative work, the electric potential energy increases, and the electric potential energy is positive; Move a negative charge from infinity to a certain position of the positive charge electric field, the direction of the electric field force is the same as the direction of displacement, the electric field force is doing work, the electric potential energy decreases, and the electric potential energy is negative; So at any point in the electric field of the positive charge, the potential energy of the positive charge is always greater than that of the negative charge.

The electric potential energy is relative, if the infinity potential is taken as 0, then the potential of any point in the electric field of the positive charge is positive, and the potential energy of the negative charge at any point is negative.

However, if the electric potential at the distance positive charge r is 0, then the electric potential greater than r is negative, and the potential energy of the negative charge at these positions is positive.

So the above sentence is wrong.

We live with a sea level of 0 points.

In the electric field, we specify: infinity is the zero point of electric potential.

We also have the knowledge that the electric potential decreases gradually along the direction of the electric field lines.

Positive charge: The direction of the electric field line is directed by the positive charge to infinity, and the electric potential along the direction of the electric field line gradually decreases, and the electric potential at infinity is 0, indicating that the potential generated by the positive charge is positive to the negative charge: The direction of the electric field line points to the negative charge from infinity, and the electric potential along the direction of the electric field line gradually decreases, and the electric potential at infinity is 0, indicating that the potential generated by the negative charge is negative.

The potential zero point of the charge is at infinity.

The direction of the power line of the positive charge is from the point charge to infinity, so it is positive everywhere.

The direction of the negatively charged power line is directed from infinity to the position of the point charge, so it is negative everywhere.

This is prescriptive and needs to be remembered, as if we prescribe 1+1=2.

Formula for the electric potential around the midpoint charge in vacuum.

kq r (take infinity as 0 equipotential surface).

Around the positively charged object, its potential must be positive, and the farther away from the charged body, the lower the potential.

When not otherwise specified, the electric potential at infinity is generally defaulted to 0, then this sentence is correct, according to the electric potential energy e= q: the electric potential energy of the positive charge and the negative charge at infinity are both 0, the electric field line around the negative charge of the field source is directed to the negative charge from infinity, the electric potential in the electric field decreases along the direction of the electric field line, the potential energy of the positive charge along the electric field line e= q decreases, and the electric potential energy at any point in the electric field is negative;

The potential energy of the negative charge along the electric field line e= q increases, and the potential energy is positive at any point in the electric field.

As the positive and negative representations of electric potential energy represent magnitude.

Hence the phrase: "At any point in the electric field produced by a negative point charge, the potential energy possessed by a positive charge must be less than that possessed by a negative charge".

But if any other point in the electric field (non-infinite) is taken as 0 potential energy point, this sentence is wrong, and the judgment method (three sentences):

The electric potential in the electric field decreases along the direction of the electric field line;

The potential energy of the positive charge along the electric field line decreases, and the potential energy of the negative charge along the electric field line increases.

The positive and negative of the electric potential energy represents the magnitude.

If this sentence is not strict, when I teach the students, I must first explain the prerequisites, and take the electric potential at infinity as 0

Under such conditions, the potential of a point in the electric field caused by a negative charge is 0 at infinity.

So the electric potential of other points decreases along the direction of the electric field line, that is, the electric potential energy of a positive charge less than 0 at a certain point is the electric potential of the positive charge +q multiplied by the electric potential of the point -u, so the electric potential energy is negative and less than 0

The potential energy of the negative charge at that point is the charge of the negative charge -q multiplied by the potential -u at the point, so the potential energy is positive, and if it is greater than 0, then the potential energy of the negative charge is greater than the potential energy of the positive charge.

There is this in multiple-choice questions, but it is generally not said that the premise is 0 at infinity, so many students are confused.

We usually choose that the electric potential at infinity is zero, and according to the decrease along the direction of the electric field line, the electric potential of any point in the electric field generated by the negative point charge is negative, then according to the electric potential energy e= q, we can know that the electric potential energy of the positive charge is negative, and the electric potential energy of the negative charge is positive, so the potential energy of the positive charge is less than the potential energy of the negative charge.

Regardless of the type of charge, the work done by the electric field force of the moving charge on the charge = decrease in the potential energy of the charge = the potential energy of the charge at a certain position minus the potential energy of the charge at the initial position.

Let there be two points A and B in the electric field, and the potential of A is higher than the potential of point B: (a) > b) The positive charge moves from A to B, and the potential energy decreases, that is, from the position of high potential energy A, the potential energy decreases to B, so the higher the potential of A, the greater the potential energy of the positive charge;

Similar analysis: when the negative charge moves from b to a, the electric field force does positive work, and the potential energy decreases, and the lower the b potential, the greater the potential energy.

1.From the formula "Electric potential."

Energy e = amount of electric charge.

Q potential", the amount of charge of a negative charge is negative, so it is the opposite of the case of a positive charge.

2.From the analysis of the electric field line, the electric potential becomes smaller along the direction of the electric field line, and the situation is the same.