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!

Homework Help: Magnetic Field of Power Lines

  1. May 13, 2015 #1
    1. The problem statement, all variables and given/known data

    You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that the two wires run about 30 m above the ground and about 2.9 m apart. A call to the local power company provides the information that the lines operate at 10 kV (rms) and provide a maximum of 44 MW to the local area. Estimate the maximum magnetic field you might experience walking under these power lines.

    2. Relevant equations

    B=mu0*I/2 pi r

    3. The attempt at a solution

    Would I be able to find the current from the given power and voltage?

    Power = V^2/I where V is the voltage (10kV) and I is the unknown current and power is 44 MW

    Then using that to find the magnetic field

    B=mu0*I/2 pi r

    and I'm not sure which value for r to use? Would it be 2.9m/2 because it's the radius I'm interested in?

    Thanks in advance!
  2. jcsd
  3. May 13, 2015 #2


    User Avatar
    Homework Helper

    The formula for the power is wrong.
    You are interested in the magnetic field at your place, on the ground. How far are you from the power lines?
  4. May 14, 2015 #3

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Remember you have 2 line with current traveling in opposite direction. There will need to be a vector superposition of the two lines' currents.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted