Here are a few terms that are frequently used when we talk about AC, that is, Alternating Current. Some of them are used when talking about Direct Current as well.
Introduction
In some of the other articles, we have read about current electricity. There is also static electricity. Here, we will read about the type of electricity that we call alternating current, or simply AC.
The alternative to AC is DC, or Direct Current. In DC, the current flows in only one direction — from the positive to the negative terminal of a battery, cell, or DC generator. DC can also be generated using a solar photovoltaic cell. Coming back to AC, as the term says, current is alternating. It means that direction of flow of current alternates.
If we plot the graph of current flowing through a circuit with an AC source, it is in the shape of a wave. This wave is called sinusoidal wave, or sine wave, in short.
In AC, both the current and the voltage rise and fall in the form of a sine wave. The positive part is upper part of the wave, while negative voltage or current is in the lower part.
Some AC Terms
Cycle: It means one complete wave from 0o to 360o.
Period (T): It is the time taken for one complete cycle. It is measured in seconds (s).
Frequency (f): The number of cycles in one second is called the frequency of the wave. It is measured in hertz (Hz). The frequency of power in India is 50 Hz. It means that there are 50 cycles of voltage and current in each second. Frequency of power in USA is 60 Hz.
Peak/Maximum/Amplitude (Vm): It is the highest value attained by the wave in positive or negative direction.
How is AC voltage or current measured?
If the current keeps changing continuously, how is it measured? We know that DC is steady and it is easy to measure. But AC value of current and voltage is never still and rises and falls in the form of a sine wave. There is a method to measure AC values. It is called RMS value. RMS stands for Root Mean Square.
To measure AC, it is compared with DC. Both DC and AC forms of electricity produce heat. A certain value of DC current produces a certain amount of heat when passed through a conductor for a fixed amount of time. The amount of AC current that produces the same amount of heat when passed for the same amount of time is the RMS value if the current.