Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Power loss in transmission lines (Electromagnetic Induction and Faraday's Law)

  1. Mar 20, 2006 #1
    Show that the power loss in transmission lines, PL, is given by PL = (PT)^2 X R/(V^2), where PT is the power trasmitted to the user, V is the delivered voltage, and R is the resistance to the power lines.

    I don't even know where to start. Im so confused by this chapter, I don't know what this question has to do with magnetic flux and Lenz's law and the other stuff in the chapter. Any help please?? :surprised
  2. jcsd
  3. Mar 20, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    It has nothing to do with Lenz law or flux, indeed.

    Think of a simple circuit with two resistors (representing the resistance of the line and the resistance of the load (where the user is drawing power from).

    You have [itex] P_L = R_1 I^2 [/itex] and [itex] P_T = R_2 I^2 [/itex] where [itex] R_1[/itex] is the resistance of the lines. You also have [itex] V = R_2 I [/itex] where V is the voltage delivered to the user. Use the last two equations to isolate I and plug in the first and you will get the answer. (also, you could use directly [itex] P_T = V I [/itex] which gets you to the answer faster).

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook