Induction current was for the first time found in 1824 by the Oersted. In seven years Faraday and the Henries developed and added his theory. Such current is used for assessment of durability of designs and materials, and therefore knowledge of it is very important for the modern industry and the engineering industry.
Induction and current
When passing the conductor through magnetic field in it there is current. It occurs thanks to the fact that power lines of the field force free electrons to move in the conductor. Such process of generation of current by means of changeable magnetic field is called induction.
One of conditions of emergence of electromagnetic induction, is that the conductor has to be perpendicular to power lines of magnetic field for the purpose of obtaining the maximum force of impact on free electrons. The direction, courses of current is defined by orientation of power lines and the direction of movement of a wire in the field.
If through the conductor pass alternating current, then changes of magnetic field will coincide with fluctuations of electric current on a phase. Also increase and decrease of magnetic field can induce electric current in other conductor which is under the influence of this field. Current parameters in the second wire will resemble the first. To increase amplitude of alternating current, the conductor is reeled up around the magnetic core. Thus, magnetic field becomes localized in a cylinder or a Torah. It repeatedly increases a difference of potentials on the ends of the coil. It is considered that induction current always proceeds on a blanket, but not in the conductor. Also very much often such current is circulating and closed. To understand it, it is necessary to present a whirlpool or a whirlwind. Thanks to this similarity, electric currents of this kind were called vortex.
Use of vortex currents
Detection and measurement of tension of the magnetic fields created by vortex currents allows to study conductors in case there is no opportunity to investigate them by usual methods. For example, the conductivity of material can be defined by force of vortex currents which are formed in it under the influence of magnetic field. It is possible to determine by the same method microscopic defects of substance. Cracks and other roughnesses on the surface of material will prevent formation of vortex currents in such area. It is called vortex-current control of a razrushayemost of material. Technicians and engineers use such control to find roughnesses and defects of the fuselages of planes and various designs which are under big pressure. Such checks become with a certain frequency, each material has the threshold of fatigue and at its achievement it is necessary to replace a detail new.