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: Magnitude and Direction of a Magnetic Field at the Circumference of a Disk

  1. May 2, 2012 #1
    1. The problem statement, all variables and given/known data

    A very thin disk of non-conducting material initially holds a charge QO = +5 μC that decreases with time t as

    Q(t) = QO e-t/τ
    where τ = 10 seconds.
    If the disk has a radius of 0.10 m, what is the magnitude and direction of the magnetic field at the circumference of the disk as a function of time?

    2. Relevant equations
    Assume at any time t that the displacement vector D is uniform across the disk.
    There is no free current.

    ∇[itex]\bullet[/itex]E = (1/εO

    ∇×B = μOJ + μOεO (∂E/∂t)
    3. The attempt at a solution

    I tried to just work out the curl of B and I immediately ran into problems and it's not correlating to the problem.
    Last edited: May 2, 2012
  2. jcsd
  3. May 2, 2012 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Show your work. Don't just describe what you did generally.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook