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!

Current through two different types of wire of different diameter

  1. Nov 9, 2011 #1
    1. The problem statement, all variables and given/known data

    For what electric field strength would the current in a 2.0 mm diameter nichrome wire be the same as the current in a 1.0 mm diameter aluminum wire in which the electric field strength is 0.0080 V/m?

    aluminum diameter = 1.0 mm
    Same current(I) flowing through both wires

    2. Relevant equations

    J = sigma*E........ I/A = sigma*E
    so.....I = sigma*E*A
    sigma = 1/rho
    sigma = conductivity; rho = resistivity

    3. The attempt at a solution

    Equating the two currents, I solved for the unknown E-field:

    E(nichrome) = (E*A*sigma(aluminum))/(A*sigma(nichrome))
    rho(nichrome) = 1.1*10^-6 Ωm
    rho(aluminum) = 2.82*10^-8 Ωm

    I calculated the E-field to be approximately 0.078 V/m, but this was apparently wrong. Help would be appreciated..!
     
  2. jcsd
  3. Nov 9, 2011 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Show us the steps you took, so we can help you.
     
  4. Nov 9, 2011 #3
    Really? All I did was "Equate the two current equations"......
    So here it is:

    σEA = σEA

    The left side representing Nichrome, and then the right side representing aluminum. Then I solved for the E-field of the unknown wire getting:

    E = (σEA)/(σA)

    The top part of the fraction being aluminum properties, and the bottom being the properties of Nichrome. Is there anything that I have done wrong????
     
  5. Nov 9, 2011 #4

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Your derivation was correct, I got the same result. What is the problem with it?

    ehild
     
  6. Nov 9, 2011 #5

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    How are the two areas related?
     
  7. Nov 9, 2011 #6
    The homework website says my answer of 0.078 V/m is wrong. I'm utterly confused. I'll have to address my professor about this problem, as well as the other problem. I've double checked every single possible error for units, etc. as well.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Current through two different types of wire of different diameter
Loading...