What is the magnetic field?To answer this question, let us recall the foundations of electrodynamics.As is known, on a stationary carrier charge q, arranged in the area of electric field, it appears to effect a biasing force F. The more charge value (regardless of their properties), the greater the force.It is a tension - one of the properties of the field.If we designate it as E, then we get:
E = F / q
In turn, mobile charges affect the magnetic field of nature.However, in this case the force depends not only on the quantity of electric charge, and the vector direction of movement (or, more precisely, speed).
How can examine the configuration of the magnetic field?This problem was successfully solved the well-known scientists - Ampere and Oersted.They were placed in the conductor circuit with an electric shock, and studied the intensity of affects.It turned out that the result has influenced the orientation of the contour in the space, indicating the presence of the vector direction of the torque.The induction of the magnetic field (measured in Tesla) is expressed by the ratio of said moment of force to the product of the area of the conductor circuit and the flow of electric current.In fact, it describes the field itself, which in this case is also necessary.Express what has been said by a simple formula:
B = M / (S * I);
where M - the maximum torque depends on the orientation of the loop in a magnetic field;S - total area of the circuit;I - current in a conductor.
Since the magnetic field is a vector quantity, is further required to find its focus.The most visual representation of it gives ordinary compass needle that always points to the north pole.Induction of earth's magnetic field orients it according to the magnetic field lines.The same occurs when placing the compass near a conductor through which current flows.
Describing the circuit, it should introduce the concept of the magnetic moment.This vector is numerically equal to the product of S by I. Its direction is perpendicular to the plane of the conventional conductive circuit.You can determine the well-known rule of the right screw (or thumb, that one and the same).The magnetic induction in the vector representation coincides with the direction of the magnetic moment.
Thus, we can derive a formula for the force acting on the circuit (all values vector!):
M = B * m;
where M - total vector moment of the force;B - magnetic induction;m - magnetic moment.
No less interesting is the magnetic field of the solenoid.It is a cylinder with the wound wire through which an electric current.He is one of the most used elements in electrical engineering.In everyday life, with solenoids each person faces constantly, even without knowing it.Thus, the current generated by the magnetic field inside the cylinder is completely homogeneous, and its vector is directed coaxially with the cylinder.And here is the body of the cylinder magnetic induction vector is missing (zero).However, this is only true for a solenoid with an ideal of infinite length.In practice, the limit is different.First of all, the induction vector is never equal to zero (the field is recorded in and around the cylinder), and the internal configuration also loses its homogeneity.Why, then, need the "ideal model"?Very simple!If the diameter is less than the length of the cylinder (usually it is), then the center of the solenoid induction vector is almost identical to that characteristic of the ideal model.Knowing the diameter and length of the cylinder, it is possible to calculate the difference between the induction coil and its end ideal (infinite) counterpart.Typically, it is expressed as a percentage.
