AC circuit doubts

  • Thread starter dhruv.tara
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  • #1
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Main Question or Discussion Point

Now this is not a homework question, just a practise question and my answer doesn't match.

An AC source of 200 V rms supplies active power of 600 W and reactive power of 800 VAR. The rms current drawn from the source is ? (the answer is 3.75 while mine is 5)

I did was squared and added the powers to get V^2*I^2, plugged in the value of V and got I as 5... Any help?
 

Answers and Replies

  • #2
vk6kro
Science Advisor
4,081
40
I like your answer.

Try it with 24 ohms resistive and 32 ohms reactive in series.
I squared R:
5 * 5 * 24 = 600 watts
I squared X
5 * 5 * 32 = 800 VAR

resultant of r + x:
SQ rt of (24 * 24 + 32 * 32) = 40 ohms
200 V / 40 ohms = 5 amps
 
Last edited:
  • #3
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p=sqrt(3)*V*I*p.f
 
  • #4
46
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from where did that sqrt(3) factor come into? I have seen this factor before, but as far as I remember that was in 3 phase systems... And I am not dealing with such problem yet I think...
 
  • #5
21
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sorry, my mistake, you're right dump the sqrt(3).
 
  • #6
46
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hmm okiess... thanks all
 

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