Initially, electricity and magnetism were studied separately, as Greek philosophers thought that these two branches of physics were unrelated. However, after Cristian Oersted's experiments it was possible to verify that electricity and magnetism did have a relationship. In his experiments, Oersted was able to prove that a wire covered by an electric current generated a magnetic field around it. This proof came through the movement of a compass needle.
Oersted placed a compass next to a conductor covered by an electrical current and found that it oriented itself in a different direction from the direction it assumed when the electric current in the thread.
After several studies, it was found that the electric current produces a magnetic field proportional to the intensity of the current, that is, the more intense the electric current that runs through the wire, the greater will be the magnetic field produced at your return.
We can determine the direction of the magnetic field around the conducting wire through a simple rule known as
right hand rule. In this rule we use the thumb to indicate the direction of the electric current and the other fingers indicate the direction of the magnetic field.
The intensity of the magnetic field generated around the straight conductor wire is given by the following equation:
Where μ is the physical quantity that characterizes the medium in which the conducting wire is immersed. This magnitude is called magnetic permeability of the medium. The unit of μ, in SI, is T.m/A (tesla x meter/ampere). For vacuum, the magnetic permeability (μO) is, by definition:
μO = 4π.10-7T.m/A
Let's look at an example:
Suppose we have a wire traversed by a current with an intensity equal to 5 A. Determine the magnetic field from a point 2 cm from the wire.
We calculate the field using the equation above, so we have that the quantities involved in the example are: i = 5 A, R = 2 cm = 2 x 10-2 m. Let's calculate.
By Domitiano Marques
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/campo-magnetico-gerado-por-um-fio-condutor.htm
