# RMS Value of AC Signal

**Why is ** **RMS value used in AC systems? **

**What does it means and mean?**

**Why aren’t all AC system ratings average in RMS?**

**What is the difference between RMS and average?**

**These are the questions that come to mind every time we look at alternate circuits.**

**Suppose we have a simple continuous circuit (Figure 1) and want to play them in a switch circuit. **

**We all have the same characteristics, except for the supply voltage, which now has to be an alternative supply voltage. **

**Now the question arises, what should be the AC voltage so that our circuit works the same as that of the DC.**

**Take the same value for the AC supply voltage (AC Vpeak = 10 volts) as in our DC circuit. **

**In this way, we can see for half a cycle (Figure 3) that the AC signal does not cover the entire range (blue range) of the constant DC voltage,**

** which means that our AC signal can not deliver the same power as our DC power supply.**

**This means that we need to increase the AC voltage to cover the same**

** range and see if it delivers the same amount of energy or not.**

**We have found that (Figure 4), by increasing the peak Vpeak voltage to **

**(p / 2) times the DC supply voltage, the entire AC-DC voltage range can **

**be covered. **

**When the AC signal completely represents the DC signal, this DC signal **

**value is referred to as the average value of the AC signal. Root Mean Square**

**Our AC voltage should now deliver the same amount of energy. However, when we turned on the power supply surprisingly, we found **

**that the AC voltage supplied more power than the DC voltage.**

** Because an average AC value provides the same amount of charge, but not the same amount of energy. **

**To get the same amount of energy from our AC power supply, we need to reduce our AC supply voltage.** **Root Mean Square** **or RMS value**

**We have found that by reducing the Vpeak peak voltage to 2 times the**

** DC voltage in both circuits, the same current flows. **

**If the AC signal supplies the same amount of energy as DC, this DC **

**value will be referred to as RMS or AC.** **Root Mean Square** **or RMS value**

**We are always concerned about the amount of energy that flows **

**through our circuits, no matter how many electrons are needed to drive them. **

**For this reason, the AC RMS value is always used in the whole AC**

** th**e **system instead of the average or RMS value.**

## Conclusion of RMS value

**The average value of an alternating current represents the same number of DC loads.**

**The rms value of an alternating current corresponds to the direct current quantity**

**AC requires less load to deliver the same amount of DC power.**