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!

Electric field on a disk

  1. Jan 6, 2010 #1
    1. The problem statement, all variables and given/known data

    A charge of -5.00 nC is spread uniformly over the surface of one face of a nonconducting disk of radius 1.15 cm. Find the magnitude of the electric field this disk produces at a point P on the axis of the disk a distance of 3.00 cm from its center.

    2. Relevant equations

    Surface area element for a disk [sigma]= Q / A

    See attachments

    3. The attempt at a solution

    So I plugged the numbers in accordingly, had no luck.

    I appreciate the help.

    Attached Files:

    • 1.jpg
      File size:
      55.9 KB
    • 2.jpg
      File size:
      47.9 KB
  2. jcsd
  3. Jan 6, 2010 #2
    I'm working on uploading a picture of my attempt.
  4. Jan 6, 2010 #3
    ... uploaded

    Attached Files:

    • 3.jpg
      File size:
      68.2 KB
  5. Jan 6, 2010 #4


    User Avatar
    Homework Helper

    That equation only applies for infinitely large plates. This disk is not infinitely large.

    Try using E=kq/r^2 to get the electric field due to the charge on one infinitely thin ring surrounding the center of the disk. Then, integrate over the disk.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Electric field on a disk