What is Root Mean Square (RMS) Value?

What is Root Mean Square (RMS) Value?

In this article, we will explain the concept of root mean square. One way to express the magnitude of a variable current or voltage is to specify its width. But the amplitude gives us the peak value of current or voltage. Sometimes it is more useful to know the average value. So getting the average of all the values does not help us.

When the average of a periodic sinusoidal signal voltage is taken, the voltage value of the positive half cycle is destroyed by the negative half cycle voltage values. Therefore, the average voltage value will be zero.

To avoid this result, an operation is performed using the fact that all the numbers are positive. To find such an average value, a special mathematical method is used to square the thousands of voltage values recorded over a period. Then the squares are averaged. Finally, the square of the middle is taken.


The average of the resulting mean values is called the square root of the average or the RMS value. RMS comes from the initials of the English Root Mean Square expression. The RMS value of a sinusoidal signal is 0.707 times the peak amplitude. In other words, the peak amplitude of a sinusoidal signal is 1.4 times the RMS value.


To give an example;

When the mains voltage is 230 V, we say RMS value. The peak amplitude is 1.4 x 230 = 322 V. One important case here is that the peak amplitude can take a value of + 322 V. For this reason, this should be considered when choosing the elements used in circuit designs.

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SEE ALSO: What is Alternating (AC) Current?

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