The magnetic field can be created by the motion of charged particles, an alternating electric field or the magnetic moments of particles (permanent magnet).
The magnetic and electric fields are manifestations of one common field - electromagnetic.
An ordered motion of charged particles
An ordered motion of charged particles inconductors called electrocution. To obtain it you need to create an electric field with the help of current sources to do work on charge separation - positive and negative. Mechanical, inner or any other energy source is converted into electrical energy.
For some events, you can judge the presence of current in the circuit
The movement of charged particles in a conductorcan not be seen. However, to judge the presence of current in the circuit can be on circumstantial evidence. Such phenomena include, for example, thermal, chemical and magnetic action of the current, the latter being observed in any of the conductors - solid, liquid or gaseous.
As a magnetic field
Around any current-carrying conductor existsa magnetic field. It is created by moving electric charges. If the charges are fixed, they produce only around itself an electric field, but as soon as there is current, there is also a magnetic field of the current.
How is it possible to detect the existence of a magnetic field
The existence of a magnetic field can be detecteddifferent ways. For example, you can use for this purpose a small iron filings. In a magnetic field, they are magnetized and converted into magnetic arrows (as in a compass). The axis of each of these arrows is set in the direction of the magnetic field strength.
The very experience looks like. Pour a thin layer of cardboard on iron filings, skip through it straight conductor and switch current. You will see how under the influence of the magnetic field of the current dust will settle around the conductor in concentric circles. These lines, along which the magnetic direction, called the magnetic lines of the magnetic field. "North Pole" arrows at each point in the field is considered to be the direction of the magnetic line.
What are the magnetic lines of the magnetic field produced by the current
Magnetic lines of the magnetic field current - isclosed curves, covering the conductor. With their help it is convenient to represent the magnetic field. And, since the magnetic field is in all points of the space around the conductor, through any point of the space can hold a magnetic line. The direction of magnetic lines depends on the direction of the current in a conductor.