alternating electrical current - current with the changing time and the direction of force.Those currents that vary only in size, called pulsing.In industry and everyday life is most often used alternating sinusoidal current.
Converting DC to AC electric can be performed as follows.Placed in a uniform static magnetic field coil of wire.At uniform rotation around the axis of the coil magnetic flux will continuously vary in magnitude and direction.Consequently, by the law of electromagnetic induction, a coil is formed variable in direction and magnitude of the electromotive force (EMF).If such a coil connected to an external circuit, then it we obtain an alternating electrical current.
When the plane of the rotating coil becomes perpendicular relative to the field lines of the magnetic field passing through her magnetic flux - the largest (Φ = Φmax), the speed of the change of its zero (ΔΦ / Δt = 0), since passingthrough such a situation, the conductors round slip of field lines, without crossing them.So, the induced emf, which is formed in the coil will be equal to zero (E = 0).
When the plane of parallel field lines, flux penetrating it, is zero (Φ = 0), the speed of the changes it in this position largest ((ΔΦ / Δt) max), as wires coil moves perpendicular to the field lines.
emf arising in this case, the coil has the greatest value (E = Emax).Upon further rotation of the rate of change of flow coil, piercing round, will increase;It means the absolute value of emf will increase from 0 to Emax.Thus, the level of EMF in a rotating induction coil at one of its turnover varies from -Emax to + Emax.
us open coil of wire and attach it to the oscilloscope.When the coil rotates in a magnetic field, the oscilloscope will record all changes of the current, which can be judged, and the change of the electromotive force in the coil during one rotation.
current generated in the coil during its uniform treatment in a uniform magnetic field, as shown by waveform varies sinusoidally.This current is called alternating sinusoidal.
interval of time during which the electromotive force performs one oscillation, called the period of the AC.
letter designation of the oscillation period - T. The number of oscillations per second 1 - frequency current, which is denoted by the letter f.Its unit of measurement - Hertz (Hz):
f = 1 / T, or T = 1 / f.
If the voltage in some arbitrary time is denoted by e (its instantaneous value), and the largest value (peak) - through Emax, the law expressing the dependence is, from time to time, in the case of sinusoidal current can be expressed as the following expression:
e = Emax˖sin (2 / T) t.
In most countries, industrial and residential use alternating electric current with a frequency of 50 Hz, the duration of the period of 0.02 seconds.
Getting alternating electrical current from the mechanical energy is performed using special machines, which are called generators.The principle of their work - the law of electromagnetic induction.The simplest diagram of a can be represented as a frame rotating around the axis in a magnetic field of an electromagnet or permanent magnet.When you rotate the frame it forms a variable electromotive force.By connecting the frame to an external circuit, we obtain an alternating electrical current.AC generator having a stationary magnet system and rotating coils, built quite rare.
almost all such generators winding (anchor) is set stationary and the magnet system (inductor) is rotated.The real estate part of the generator is called the stator and movable - the rotor.
