Transmission cable problem involving power loss

[hendrix7]

Homework Statement

A transmission cable transmits electricity at 250A and 400kV and a resistance of 3 ohms. What is the power loss?

Relevant Equations

P = I^2R
V = IR

Using P = I²R
250² x 3 = 187.5kW
Now, I'm pretty sure that this is correct but my question is how does V = IR fit in with this? So, I = 250 and R = 3 so V must be 750, but what does this 750 volts represent? A voltage drop between two points on the transmission cable? If so, where are the two points on the transmission cable that correspond to this potential difference? Am I missing something here? This is pretty new to me so I would much appreciate it if someone could put me straight here or clarify for me.

 

[berkeman]

The input voltage of 400kV is reduced slightly at the far end by the resistive losses. The 750V drop is for the 2-way wire voltage drop from source to destination. You should get the same power loss if you do either calculation, using $I^2R$ loss or $\frac{V^2}{R}$ loss.

 

[hendrix7]

The input voltage of 400kV is reduced slightly at the far end by the resistive losses. The 750V drop is for the 2-way wire voltage drop from source to destination. You should get the same power loss if you do either calculation, using $I^2R$ loss or $\frac{V^2}{R}$ loss.

Thank you, berkeman, that seems clear to me now. I really appreciate that.