Significance of Average value of a AC signal

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Discussion Overview

The discussion centers on the significance of the average value of an AC signal, particularly in the context of sinusoidal sources and their behavior in circuits with resistors. Participants explore the relationship between average values, RMS values, and their implications in different scenarios, including full wave rectified signals.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant queries the significance of the average value in an AC circuit, noting that the RMS value indicates the equivalent DC value that dissipates the same heat.
  • Another participant states that the average value of a sinusoidal wave is zero, suggesting it represents the DC component of the signal.
  • A participant questions the meaning of the average value when only the magnitude is considered, specifically in the context of a full wave rectified signal, asserting it does not represent the DC value as the RMS does.
  • One participant explains that the average value can be seen as the DC offset of an AC signal, providing an example of a sine wave with a DC offset.
  • A later reply clarifies that the RMS value represents the equivalent DC source that would output the same power as the sinusoidal source, and discusses the Fourier series representation of a rectified wave.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of average values in AC signals, particularly regarding their significance in relation to RMS values and rectified signals. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

Some participants highlight the need to consider the DC offset in AC signals and the implications of rectification, but the discussion does not reach a consensus on the significance of average values in all contexts.

spiky
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[SOLVED] Significance of Average value of a AC signal

Hello,
I would like to know the significance of average value in a AC circuit. Let's consider a sinusoidal ac source with only a resistor in the circuit. The rms value of voltage and current indicate the equivalent DC value which would dissipate the same heat in the same circuit. So on similar terms what will the average value signify ?

Thanks
 
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spiky said:
Hello,
I would like to know the significance of average value in a AC circuit. Let's consider a sinusoidal ac source with only a resistor in the circuit. The rms value of voltage and current indicate the equivalent DC value which would dissipate the same heat in the same circuit. So on similar terms what will the average value signify ?

Thanks

The average value of a signal is the DC component of the signal. In a sinusoidal wave the average value is zero.
 
ofcourse, but what will it be if only magnitude is considered ? . What will the average value represent in a full wave rectified signal ?
It certainly does not represent DC value as rms value does that.
 
The average value is just the DC offset of the AC signal. A sine wave signal can have a DC offset. For example, like this:

v(t) = 2.5V + 2.5V cos(wt)
 
This has a good explanation of both and also a comparison and why some applications use RMS and others use just average

http://www.allaboutcircuits.com/vol_2/chpt_1/3.html
 
spiky said:
ofcourse, but what will it be if only magnitude is considered ? . What will the average value represent in a full wave rectified signal ?
It certainly does not represent DC value as rms value does that.

No, rms represents the value of a DC source that would output the same power as the sinusoidal source.
A rectified wave can be thought as the combination of a DC source (the mean value) and an infinite number of sinusoids with frequencies that are the harmonics of the original sinusoid. The Fourier series of the wave shows exactly this.
 
thanks a lot guys.
 

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