We know that as we move away from the charge producing the electric field, the strength of this field decreases. However, we do not yet understand how this variation occurs. So let's look for an equation that allows us to relate the field strength to the source electrical charge, the medium, and the distance.
Let us consider the point source charge Q, in a vacuum, and a proof load what, separated by a distance d. Being P the geometric point where the test load is located, as shown in the figure above.
We have the following equations:
Substituting equation 1 into equation 2 we have:
The equation shows us that:
- the strength of the electric field is inversely proportional to the square of the distance from the point P to source load Q.
- the strength of the electric field in P does not depend on the proof load value what, as this was canceled in the above deduction.
- the field strength depends on the environment surrounding the source load.
Let's see the example below:
A point-shaped electrical charge Q = 3 x 10-10 Ç generates, in a vacuum, an electric field. Determine its intensity within 3 mm of it. adopt k0 = 9 x 109 SI units.
Resolution:
We must make d = 3 mm = 3 x 10-3 m, to work on the SI.
By Domitiano Marques
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/campo-eletrico-uma-particula-eletrizada.htm