Transmission Line, voltage drop

[stickman!]

Homework Statement

Prove that for a line having resistance R, and reactance X, and supplying load of P+jQ has an approximate voltage drop of:

Vr = [RP+XQ]/Vs

Homework Equations

none given.

The Attempt at a Solution

I made a diagram, with R, X, and P+jQ in series. Vr is the potential drop across the load, and Vs is the supplying voltage. I've tried every method, but it doesn't turn out to be the given answer. I've covered two pages worth of pointless calculations, and it just doesn't seem to work out.

help me as soon as possible.

thanks :)

-peace
stickman!

 

[berkeman]

Homework Statement

Prove that for a line having resistance R, and reactance X, and supplying load of P+jQ has an approximate voltage drop of:

Vr = [RP+XQ]/Vs

Homework Equations

none given.

The Attempt at a Solution

I made a diagram, with R, X, and P+jQ in series. Vr is the potential drop across the load, and Vs is the supplying voltage. I've tried every method, but it doesn't turn out to be the given answer. I've covered two pages worth of pointless calculations, and it just doesn't seem to work out.

help me as soon as possible.

thanks :)

-peace
stickman!

Welcome to the PF. I think there must be a typo in your "solution" equation:

Vr = [RP+XQ]/Vs

If I interpret your variables correctly, you are saying that units of Volts^2 = units of Ohms^2

Doesn't look right...

 

[stickman!]

Welcome to the PF. I think there must be a typo in your "solution" equation:

Vr = [RP+XQ]/Vs

If I interpret your variables correctly, you are saying that units of Volts^2 = units of Ohms^2

Doesn't look right...

i'll look over it, but that's what it says on the question paper.

thank you for pointing it out, i should've noticed this ! :p

-peace
stickman!