Calculating Power Loss in a High Voltage Transmission Line

  • Thread starter SparkimusPrime
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In summary, the conversation is about calculating the power lost by a line with a given current, voltage, distance, and resistance. The original power is found to be 7e8 watts, but due to a math error, the final power is incorrectly calculated as 5e7 watts instead of 6.5e8 watts. The correct answer given by the teacher is 50 MW (50e6 watts). There is a discussion about whether the teacher wants the power dissipated by the wire or the power that is left. The conversation concludes with the realization that the problem was misunderstood due to the use of obscure language in the book.
  • #1
SparkimusPrime
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0
A question surprisingly similar to this:

https://www.physicsforums.com/showthread.php?t=17219

I = 1000amp
V = 700,000volt
distance = 100miles
Resistence of the wire = .5 ohm / mile

The resistence of my line is 50 ohms, original power is 7e5 * 1e3 = 7e8 watts. Final power, due to P = (I^2) * R, is 1e3^2 * 50 = 5e7 watts

So finding the difference:

7e8 - 5e7 = 6.5e8

The answer given by the teacher is 50 MW (50e6 watts right?). A math error I'm sure, anyone see it?

Peter
 
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  • #2
I am not sure why you are computing the difference.

The power lost by the line is

P=I2R

End of story, you do not even need to know the total power transmitted.
 
  • #3
Maybe your teacher wants the power dissipated by the wire, and not the power that is left?

Beat me to it. :smile:
 
  • #4
Yes sorry, read the problem wrong. Seems to be a common failing with this book, using obscure english to mask the real problem.

Thanks.

Peter
 

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