study of a variety of magnetic phenomena has shown that wherever there is an electrical current, ieelectric charges are in motion, there is a current and a magnetic field.
Due to the fact that the magnetic field is formed around a conductor when a current flows in the latter, it is often seen as a source of formation of a magnetic field.In this sense, it is called "the magnetic field of the current."
His direction regardless of the direction of the electric current, around which there is a field.
The existence of a magnetic field around the conductor with an electric current is possible to detect a number of ways.One of these methods is the use of iron filings.Once in the magnetic field of the current iron pieces that make up iron filings become small magnetic arrows.Each of the arrows in the magnetic field is set so that its axis coincides with the orientation of the magnetic field at the location where it is.With many such arrows, you can see how the direction of the forces acting in the magnetic field at the point of transition from one field to another.This arrangement in the magnetic field of the current iron filings called magnetic spectrum.
use the magnetic filings and consider the magnetic field of direct current.To do this, skip the conductor through a sheet of cardboard, and paperboard sprinkle a thin layer of iron filings.We note that when a current is passed through the conductor saw dust will settle around it in concentric circles.
lines on which the magnetic field axis current has tiny magnetic arrows call it power lines.With the power lines it is very convenient to depict graphically the magnetic field.
Power line is drawn in such a way that the tangent to it at any point indicates the direction of the force acting at this point to the North Pole.
chains formed in the magnetic field current using iron filings indicate what form of lines of force in a magnetic field.
lines of force in a magnetic field - is closed curves around the conductor.In particular, the magnetic field lines of direct current - it is concentric circles centered on the streamline.
to determine the direction of the magnetic lines of force in connection with the direction of the current, instead of sawdust you need to use the magnetic needle.Surrounding their current-carrying conductor, we will determine the direction of the field lines.When the change orientation of the current in the conductor to the opposite magnetic arrows rotated 180 °, which indicates a corresponding change in the direction of the field lines.
The direction of lines of force in a magnetic field associated with the direction of the current in a conductor by a simple rule proposed by the English scientist Maxwell: If the forward movement of thumb will coincide with the direction of the current in the conductor, the direction of turning the thumb with the same direction as the field lines in magneticfield existing around a conductor.
This rule is sometimes known as the rule of thumb.Let us now
conductor bent in a circle, and, having passed through it current, we again observe the location of sawdust on a cardboard, set perpendicular to the plane of the circle.We find that the magnetic field lines are no longer correct circles, but in this case, all lines are closed, bypassing the conductor, on which there is a current.Thus, the magnetic field lines are always closed around the current.
placed in different points of the magnetic field of the small arrows, you can determine the direction of the field lines.
rule of thumb applies, of course, to the circular current, but in this case it is more convenient to swap the direction of current and magnetic field.Indeed, if the thumb stick to rotate the current, the movement of its tip will show what direction is the magnetic field of a circular current.
