To reduce cost and weight, power transmission lines are made

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g98
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Homework Statement


Determine the resistance of a 30 km long wire. b. Assume that the line transfers 1000 MW of power at a potential difference of 500 kV. What is the current through the wires? c. How much power is lost during transmission? What fraction of the transmitted power is lost?

Homework Equations


R=p*l/A P=I*deltaV P=I^2*R

The Attempt at a Solution


so, for the first one i determined the resistance to be 4,23*10^14 ohm, the current through the wire is 2000A . I am not quite sure for the above values and because of that, i get weird values for the lost power in c) I would very much appreciate a bit of help with the exercise
 

Answers and Replies

  • #2
phyzguy
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The wire resistance can't be 10^14 ohms. You have done something wrong. Show us how you did the calculations of the wire resistance.
 
  • #3
gneill
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I think there must be some important information we're missing, probably given in a "part a" portion of the problem?
 
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  • #4
cnh1995
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How much power is lost during transmission? What fraction of the transmitted power is lost?
That can't be determined unless the resistance of the line is specified.
 
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  • #5
g98
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I think there must be some important information we're missing, probably given in a "part a" portion of the problem?
The thing i didn't mention is that the wire is aluminium and the diameter is 4cm
 
  • #6
g98
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The wire resistance can't be 10^14 ohms. You have done something wrong. Show us how you did the calculations of the wire resistance.
I was wondering for the formula R=p(l/A) (p being the specificity) what should be the units of the area? i though it should be m^2 but i checked in internet and in many places i saw mm^2 and i got slightly confused
 
  • #7
phyzguy
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I was wondering for the formula R=p(l/A) (p being the specificity) what should be the units of the area? i though it should be m^2 but i checked in internet and in many places i saw mm^2 and i got slightly confused
OK, You're right that the resistance is given by R=ρ(l/A). You can use any units you want as long as you are consistent. If your value for resistivity is in Ohm-m, then you would want to use m for the length and m^2 for the area. Why don't you set up this calculation and show us the values you are using and the results.
 

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