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: Copper wire magnetic field

  1. Sep 10, 2007 #1
    A piece of copper wire has a resistance per unit length of 6.40e-3 ohm/m. The wire is wound into a thin, flat coil of many turns that has a radius of 0.190 m. The ends of the wire are connected to a 12.0 V battery. Find the magnetic field strength at the center of the coil.

    R/L = 6.40e-3 ohm/m
    r = 0.190 m
    V = 12.0 V
    u0 = 4pi e -7 Tm/A
    B = ? T

    V = IR (I = V/R)
    B = u0 * n * I
    so B = u0 * n * (V/R)

    I don't know where to go from here.
  2. jcsd
  3. Sep 10, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    Start by finding L in terms of n. That may be your missing ingredient.
  4. Sep 10, 2007 #3
    n = turns/L
    L = R/6.40e-3 ?
    im lost here
  5. Sep 10, 2007 #4


    User Avatar
    Homework Helper

    Did you post the question exactly?

    What I'm thinking is... can't you arbitrarily make the coil longer, keeping the number of turns/unit length the same... but increasing the resistance... thereby lowering the current. And that would lower the magnetic field?

    So is there a unique solution to this problem?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook