1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Efficiency of Power Line Transmission

  1. Apr 28, 2010 #1
    1. The problem statement, all variables and given/known data

    4561507462_0ebfea103e_b.jpg

    2. Relevant equations

    N/A



    3. The attempt at a solution

    I have been struggling with these questions for the past week, with not much result at all. I have to study at home, through the use of various textbooks, and with no teacher to guide me through the process. I would be extremely grateful to the person who could explain each question to me step-by-step, eventually reaching the answer. Thank you in advance.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 28, 2010 #2

    berkeman

    User Avatar

    Staff: Mentor

    Re: Momentum Conservation Questions - PLEASE HELP ME!!!

    The Relevant Equations are not "N/A". For a), use the relationship between power, current and voltage. For part b), use Ohm's Law.

    Please show us your work on at least those two parts...
     
  4. Apr 28, 2010 #3
    Re: Momentum Conservation Questions - PLEASE HELP ME!!!

    OK, here is my attempt at the first two parts (I seriously cannot do the others - PLEASE help me!):

    a) watts = volts*amps

    48,000=240*amps

    a = 200 amps

    b) V=IR

    R=V/I=48000/200=240 Ohms



    PLEASE, PLEASE, PLEASE help me on the other parts!
     
  5. Apr 28, 2010 #4

    berkeman

    User Avatar

    Staff: Mentor

    Re: Momentum Conservation Questions - PLEASE HELP ME!!!

    Hint on c) -- you calculated the effective resistance of the consumer. You are given the resistance of the supply line. Use a voltage divider equation to tell you what the source voltage must be to get the target 240V at the consumer.
     
  6. Apr 28, 2010 #5
    Re: Momentum Conservation Questions - PLEASE HELP ME!!!

    Sorry, I cannot understand that - could you explain it to me in more detail please?
     
  7. Apr 28, 2010 #6

    berkeman

    User Avatar

    Staff: Mentor

    Re: Momentum Conservation Questions - PLEASE HELP ME!!!

    What do you not understand? If you are not familiar with the term "voltage divider", you could use wikipedia.org to look it up.
     
  8. Apr 28, 2010 #7
    Re: Momentum Conservation Questions - PLEASE HELP ME!!!

    Could you or someone else please just do the last three parts, explaining them as you go? That way, I would stand a chance of understanding how to do them...
     
  9. Apr 28, 2010 #8

    berkeman

    User Avatar

    Staff: Mentor

    Re: Momentum Conservation Questions - PLEASE HELP ME!!!

    Nope. We don't help you cheat here. You'll need to try another website for that feature.

    If you are willing to do some work on your own, this is a great website. If you want to be spoonfed now, and fail later, then you need to try some other websites.

    BTW, I'm going to change the title of your thread. Momentum Conservation seems a bit off-topic.
     
  10. Apr 28, 2010 #9
    Look, however you treat me on this forum, the last thing I want you to say about me is that I 'cheat'. As I have already mentioned, I have to study MYSELF, AT HOME, with only textbooks to help me - I wrote these questions out myself, because I was struggling with them and needed full explanation on them - could you please do me that favour and explain the last three parts fully? I myself should know best the way in which I learn, and that way has always been by example. So please, please show me how to do those - they should probably take around 30 seconds for a physicist of your standard.
     
  11. Apr 29, 2010 #10

    berkeman

    User Avatar

    Staff: Mentor

    When you supply power down a trasmission line (or just over a wire), there is some power loss in the wire due to I^2R loss from the current having to pass through some (hopefully low) resistance. One of the ways you minimize those losses in AC Mains power distribution is to step up the voltage for the actual transmission line, and then step it back down again at the consumer location. Why would stepping up the voltage cut down power losses in the transmission line, assuming a constant power load requirement at the consumer location?
     
  12. Apr 29, 2010 #11
    Could you please explain this concept to me, using the questions as the example? I would understand this much better if you showed me how to do it.
     
  13. Apr 29, 2010 #12

    berkeman

    User Avatar

    Staff: Mentor

    This wikipedia article should help you to understand:

    http://en.wikipedia.org/wiki/Power_transmission_line

    .
     
  14. Apr 30, 2010 #13
  15. Apr 30, 2010 #14

    berkeman

    User Avatar

    Staff: Mentor

    No can do -- it's against the rules here.

    Please go back to this hint on c). Do you know what a voltage divider is? If not, when you looked it up on wikipedia.org (or elsewhere), what about the explanation did you not understand?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Efficiency of Power Line Transmission
Loading...