Magnetic field can be created by the movement of charged particles, variation electric field or the magnetic moments of particles (in permanent magnets). Magnetic and electric fields are manifestations of one general field – electromagnetic.
Ordered movement of charged particles
The ordered movement of charged particles in conductors is called electric current. For its receiving it is necessary to create electric field by means of the sources of current making work on division of charges – positive and negative. Mechanical, internal or any other energy in a source turns into electric.
On what phenomena it is possible to judge existence of current in a chain
The movement of charged particles in the conductor cannot be seen. However it is possible to judge existence of current in a chain on indirect signs. Thermal, chemical and magnetic actions of current belong to such phenomena, for example, and the last is observed in any conductors – firm, liquid and gaseous.
As there is a magnetic field
Around any conductor with current there is a magnetic field. It is created by moving electric charges. If charges are not mobile, they produce around themselves only electric field, but as soon as there is current, also magnetic field of current appears.
In what ways it is possible to find existence of magnetic field
Existence of magnetic field can be found in different ways. For example, it is possible to use small iron sawdust for this purpose. In magnetic field they are magnetized and turn into magnetic arrows (as at a compass). The axis of each such arrow is established in the direction of action of forces of magnetic field. Experience looks so. Fill a thin layer of iron sawdust on a piece of cardboard, miss through it the direct conductor and include current. You will see how under the influence of magnetic field of current sawdust will be located around the conductor on concentric circles. These lines along which magnetic needles were located are called magnetic lines of magnetic field. North Pole of an arrow in each point of the field is considered to be the direction of the magnetic line.
What is represented by magnetic lines of the magnetic field created by current
Magnetic lines of magnetic field of current are the closed curves covering the conductor. With their help it is convenient to represent magnetic fields. And, as magnetic field is in all points of space around the conductor, through any point of this space it is possible to draw a magnetic line. The direction of magnetic lines depends on the direction of current in the conductor.