Alternating Current

What is Alternating current ?

Alternating current can be defined as a current that changes its magnitude and polarity at regular interval of time. It can also be defined as an electrical current which repeatedly changes or reverses its direction opposite to that of Direct Current or DC which always flows in a single direction as shown below.

From the graph, we can see that the charged particles in AC tend to start moving from zero. It increases to a maximum and then decreases back to zero completing one positive cycle. The particles then reverse their direction and reach the maximum in the opposite direction after which AC again returns to the original value completing a negative cycle. The same cycle is repeated again and again.

Alternating currents are also accompanied usually by alternating voltages. Besides, alternating current is also easily transformed from a higher voltage level to lower voltage level.

Alternating Current Production
Alternating current can be produced or generated by using devices that are known as alternators. However, alternating current can also be produced by different methods where many circuits are used. One of the most common or simple ways of generating AC is by using a basic single coil AC generator which consists of two-pole magnets and a single loop of wire having a rectangular shape.

In this setup, the AC generator follows Faraday’s principle of electromagnetic induction where it converts mechanical energy into electrical energy.

Application of Alternating Current
AC is the form of current that are mostly used in home appliances. Some of the examples of alternating current include audio signal, radio signal, etc. An alternating current has a wide advantage over DC as AC is able to transmit power over large distances without great loss of energy.

Alternating Current Waveform
Before we learn more about this topic, let us quickly understand a few key terms.

• The time interval between a definite value of two successive cycles is the period.
• The number of cycles or number of periods per second is frequency.
• The maximum value in both directions is the amplitude.

The normal waveform of AC in most of the circuits are sinusoidal in nature in which the positive half period corresponds with the positive direction of the current and vice-versa. In addition, a triangular or square wave can also be used to represent the alternating current waveform.

Audio amplifiers that deal with analogue voice or music signals produce irregular AC waves. Some electronic oscillators produce square or sawtooth waves.