power is measure of?

[Disha Karnataki]

the voltage got across the resistor in ac circuit whether it is the rms value or the peak value?
And the power found by digital meters do they use rms or peak value?:?:

 

[chuckey]

RMS is the voltage that has power. A peak may be of a high voltage with a high instantaneous power but a low power in the real sense of the word. Any meter that claims to read power must detect the RMS voltage and current. otherwise the meter should be a peak power meter.
Frank

 

[Disha Karnataki]

hey frank ,
i wanted this concept for doing smart meters. wherein i wanted to know the current passing through the load.so using a resistor in series with the load & using opamp i wanted to find the voltage & then current in that branch.so as u have suggested that the voltage across resistor is nothing but rms. so the voltage calculated by the resistor will be nothing but the rms voltage & hence i can directly multiply the current got by 220v (in india) & get the power.
so it's not required to find the power at every instant on the ac wave as it will always have rms voltage across it.

 

[Venkadesh_M]

That is the advantage of measuring as RMS voltage....

 

[Disha Karnataki]

s venkadesham,
that's very important feature but, if at all i have non linear loads then there would be a distorted ac sine waveform & so it would lead to incorrect assumption that across a resistor i measuring rms.(but actually it will be something else)..

 

[Venkadesh_M]

Whatever the Load is The power is Vrms*Irms *cos(pi).. So you need not to worry about the load.. Just calculate the power factor also.. Then you can use for any load. For resistive load the power factor is 1..