Alternating current

Alternating current (ac) electronics is some­what more complex than direct current (dc) electronics. Alternating current circuits, like dc circuits, have a source of energy and load in which power conversion takes place. Most of the electrical energy produced in our country is alternating current; therefore, ac systems are used for many applications. In terms of electronic circuits, there are three important characteristics present in ac circuits. These characteristics are resistance, inductance, and ca­pacitance. Also, there are two types of ac voltage—single-phase and three-phase.

Alternating Current—Alternating current is produced commercially by an AC generator, called an alternator. The prime mover, as in the case of the d-c units may be any type of engine or Turbine. This principle of electromagnetic induction states that when an elec­trical conductor is moved in a magnetic field, a voltage is induced in it. The direction of the movement determines the polarity of the induced voltage.  If the conductor is formed into a coil and rotated in the magnetic field, a voltage of alter­nating polarity is produced, that is, alternating current. It does not matter whether the conductor or the magnet moves; the motion of the conductor and the field with respect to each other produces the voltage. Voltage is picked off with sliding con­tacts, called "slip-rings”. It does not matter whether the conductor moves and the magnetic field is stationary, or vice versa, as long as there is relative mo­tion between the two.

When an ac source is connected to some type of load, current direction changes several times in a given unit of time. Remember that dc flows in one direction only. Ac voltage is measured with a VOM and polarity of the meter leads is not important because ac changes direc­tion. (Remember that polarity is important when measur­ing dc, since direction current flow's only in one direction.)

Questionnaire:

•  Explain about alternating current.