# To reduce cost and weight, power transmission lines are made

## 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

phyzguy
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.

gneill
Mentor
I think there must be some important information we're missing, probably given in a "part a" portion of the problem?

• CWatters
cnh1995
Homework Helper
Gold Member
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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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

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

phyzguy