1. Not finding help here? Sign up for a free 30min 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!

Energy of a wave in a transmission line

  1. Feb 16, 2010 #1
    1. The problem statement, all variables and given/known data

    An ideal transmission line has a characteristic impedance of Z=50 Ohms and
    v=200,000km/s propagation velocity. A sinusoidal signal with frequency f=1GHz and
    A=10mV amplitude is traveling down the line.Its total duration is 10s.What total
    energy is it carrying?

    2. Relevant equations

    P = IV
    w = 2[pi]f
    k=w/v
    V(x,t)=Re{A exp[i(wt-kx)]}
    I(x,t)=Re{A/Z exp[i(wt-kx)]}


    3. The attempt at a solution

    I drew a picture of a transmission line that terminated into to a resistor with the same characteristic impedance as the line. The sinusoidal wave was coming in from the left only. The reflection amplitude of this wave is 0, so I think I should be able to say that all the energy in the wave was "burned" off by the resistor.

    A resistor burns energy at the rate of V^2/R J/s, which I said was equal to (A)^2/(Z), the amplitude of the wave squared divided by the characteristic impedance. I then multiplied the power by 10 seconds to get the total energy dissipated by the resistor, which I calculated to be 2*10^-5 J.

    The small answer and the fact that I didn't use all the information given pretty much yells to me that I did something wrong. I imagine that time and position dependence of the voltage and current might have something to do with it, but I'm not exactly sure.
     
    Last edited: Feb 16, 2010
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted



Similar Discussions: Energy of a wave in a transmission line
  1. Hoop and Line (Replies: 0)

Loading...