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Ac circuit & Power (I)

  • Thread starter Lord Dark
  • Start date
  • #1
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Getting powers from Ac Circuit

Homework Statement


Hi guys,, need help with the following question :

The rms voltage and current of an inductive load are 110V & 10.
The frequency of the voltage waveform is 60 Hz. The instantaneous power
consumed by the load has zero average value.Calculate :
a. The real power consumed by the load.
b. The reactive power consumed by the load.
c. The power factor.
d. The frequency of the reactive power

The Attempt at a Solution


OK, first things first ,, what does the question mean by saying
The instantaneous power consumed by the load has zero average value
?? and I know that real power equal I^2 R for series & V^2/R for parallel but the problem it doesn't say if it's series or parallel ,, so my second question is how to start solving the problem ?? (Don't give me answers please just tips :smile: )

thanks in advance
 
Last edited:

Answers and Replies

  • #2
1,860
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It means that all the inductor is doing is causing a phase shift in the AC source. So the waveform will give an average voltage, current, and even power of zero.

If you decompose the complex impedance of the inductor you have a real part and an imaginary part. The real power is, just as it sounds, the real part of the power.

No idea about "power factor."

Good luck!
 
  • #3
121
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nice ,, thanks Mindscrape got the idea :smile:
 
  • #4
4,239
1
"The instantaneous power consumed by the load has zero average value" doesn't mean anything.

It's a misstatement or something; wrong in one and a half places:

The average power into the idealized inductive load is zero. The inductive load 'consumes' no power. The instantaneous power can be into or out of the load. Instantaneous power is just the power, positive or negative at any given instant, rather than over the entire AC cycle.
 
  • #5
121
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no it's useful ,, it's to determine either the real power or reactant power equal zero
 
  • #6
4,239
1
no it's useful ,, it's to determine either the real power or reactant power equal zero
Instantaneous power and average power are not the same thing. Ask when you are in class.
 
  • #7
121
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I know they are not the same thing ,, I red in the book that the reactant or real power depends on them ...
 

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