which best describes the electric field created by a positive charge?

§ 3 The electrostatic field.

Intensity of Electrostatic field

Electric charges create an electric field around it. Field - a form of existence of matter. Field to explore, to describe its power, energy, and other properties. The field produced by stationary electric charges, called electrostatic. To investigate an electrostatic field use the test point positive charge - a charge that does not distort the investigated field (does not cause redistribution of the charges). If in the field produced by the charge q, put a test charge q ₁ on it will be a force F ₁, and the magnitude of this force depends on the charge placed in the given point of the field. If put into the same point charge q ₂, then the Coulomb force F ₂ ~ q ₂, etc.
However, the ratio of the Coulomb force to the magnitude of the test charge is constant for a given point in space

and characterizes the electric field at the point where the test charge. This value is called the intensity and is a power characteristic of the electrostatic field. The field intensity is a vector quantity which is numerically equal to the force acting on a unit positive point charge is placed at a given point of the field

The direction of the intensity vector coincides with the direction of the force.
We define the field strength generated by a point charge q at a distance r from it in a vacuum

§ 4 The principle of superposition of fields.

The lines of force vector

Determine the value and direction of the field

produced by a system of fixed charges q₁, q₂ , …q_n . Net force

, exerted by the field on the test charge q, is the vector sum of the forces

, applied to it by each of the charges q_i

Dividing by q , we obtain

Principle of superposition ( overlay) fields:

Intensity

of resulting field created by a system of charges, equal to the geometric (vector) sum of the field intensities produced at this point each of the charges separately.
Electrostatic field can be represented very clearly with lines of Intensity or power lines of vector

Field line intensity vector is a curve whose tangent at every point in space coincides with the direction of the vector .

The principle of construction of power lines :

The lines of force vector begin on positive charges and terminate at negative (ie directed from "+" to "-") .
The lines of force vector approach the surface charges at right angles .

3. For a quantitative description of the vector � field lines carried out with a certain density. The number of lines of intensity running through the unit area perpendicular to the lines of intensity must be equal to the modulus of a vector .

Homogeneous is a field that has a vector in any point in space is constant in magnitude and direction , ie vector parallel to the field lines and their density is constant at all points

Inhomogeneous field

Homogeneous field

Painting lines isolated point charges

§ 4 'Dipole.

Dipole moment.

Dipole field

Electric dipole is a system of two point-of opposite charges (+ and -) at a distance ℓ.
Vector along the dipole axis (the line passing through the two charges) from the negative to the positive charge and is equal to the distance between them, called the ARM dipole

vector

coinciding with the direction of the dipole arm and the product of the charge q on the arm is called an electric dipole moment or dipole moments .