When we speak on the magnetic field, we allude to the zone about a magnet, where magnetic forces demonstrate on a needle imantada it is named as magnetic field. The connection between electricity and magnetism was not even known in 1819, the Danish physicist There Is Christian Oersted it made clear, that an electronic current was turning a needle away in his initial position imantada placed in his proximities and to to invest the sense of the current, the needle was turning aside in the opposite sense.
The magnetic field created by a current of intensity the Ist, which circulates along a rectilinear and indefinite driver, since in a point placed at a distance r from the driver it comes given by the law: Biot-Savart, where B = 2kI/r, where the constant k is equal U0/4 π, being U0 the magnetic permeability of the gap. The value of the magnetic permeability indicates the behavior of a substance submitted to a magnetic field, in which they behave as the iron, named ferromagnética, the magnetic permeability is much major than U0, in other substances little attracted by a named magnet a diamagnéticas, whose permeability magnetic is low to U0.
In case of the currents that circulate along filiform circuits (or enclosures), the contribution of an infinitesimal element of length d l → of the circuit covered by the current Ist, it creates an elementary contribution of magnetic field, d B → in the point placed in the position that aims at the vector r → at a distance r with regard to d l → the one who points in the direction of the current I:
Also in a more widespread way we have, In an approach magnetostática, the magnetic field can be determined if the current density is known j:
dV is the distinguishing element of volume.
Although it is habitual to generate magnetic fields from the current that circulates along a driver, since physically it is interesting to individualize the phenomenon to the magnetic field created by a load in movement, in such a way that two electrons inside the driver, whose value they will be proportional at the speed of the above mentioned load and inversely proportional to the square of the distance, of this form the electromagnetic action of a load can be enunciated in a following way: an electrical load creates an electrical radial field and also it moves, creating at the same time a magnetic field of direction perpendicular to his speed.
| Biot-Savart | |
|---|---|
 Jean-Baptiste Biot (1774 -1862), source of image of mastery of Wikimedia Commons, Author: Auguste Lemoine | It tackled very varied scientific fields: in electromagnetism it formulated the Law of Biot-Savart; he studied the polarization of the light; it established the scientific knowledge of the meteorites; and it realized one of the first flights in air balloon. Also it discovered the optical properties of the mineral that takes his name, the mica biotita. |
 Félix Savart (1791-1841), source of image of mastery of Wikimedia Commons | Public ó Memory on the communication of vibratory movements between the solid bodies (on 1820, sober monografía the comunicación of los movimientos vibratorios between los cuerpos sólidos), Researches on vibrations of air (1823, investigaciones sober weary vibraciones del aerie) there Memory on vibrations of the solid bodies, considered in general (1824, monografía sober weary vibraciones of los cuerpos sólidos, considerados in general). |
Think that it is necessary to know how it operates the magnetic field on the electrical current and the charges in movement, of such form if a current becomes circular for a driver placed between the poles of a magnet, the driver will move and the movement will be invested if there turns round the sense of the current, which demonstrates that the magnetic field exercises a force on the electrical current. The force that a field of intensity B exercises on a straight driver of length d placed in his bosom, because when circulating a current in the Ist, an electromagnetic force defines her in the law of Laplace in where F=I.d. B.seno of α, where α is the angle between the driver and B, this force will have a direction perpendicular to the driver and also to the magnetic field. It is necessary to take in account if a distance of this driver is different for him, which also circulates a current, the last one will feel the application of a force created by the magnetic field. The force that is exercised two drivers are equal, proportional to the product of the currents and inversely at the distance of separation between two drivers, also the intensities have the same sense, the forces will be attractive and if they have senses I contradict the forces they will have to separate them.
Bibliography
Electromagnetism for Alonso Sepulveda Soto - 2009.
Essentials of electromagnetism for engineering for David K. Cheng - 1998.
Concepts of electromagnetism - Page 201 for José Ramón Menéndez García-Hevia - 1999.
