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: Electric Feild help

  1. Sep 4, 2004 #1
    I just recently began the Electricity and Magnetism course. Having said that I'm requesting help with a general plan of attack for two homework problems, that is, conceptually understanding how to use the math on these problems.

    First problems states there is a hollow cylinder of length h and radius R, determine the electric feild at point d to the right of the cylinder (this is the axis through the center). It also states to think of the cylinder as a collection of rings and gives me nearly the same problem solved for a single ring. My question is how would I adapt the results of the ring?

    My second problem is a uniformly charged disk of radius R and charge Q. This also has the electric feild calculated along the axis through the disk. The problem asks show that the electric feild at distances x that are large compared with R approaches that of a point charge. How would I go about grappling this problem?

    What I'm essentially asking is a gameplan for these problems like, do I integrate and if so along what axis. Thanks for any help you can give me.
  2. jcsd
  3. Sep 4, 2004 #2
    This is a basic calculus problem. You know what the electric field is at a point d from the center of the ring, so all you need to do is sum for the collection of rings (i.e. integrate).

    Easy. Find the equation for the electric field at a distance r from the center of the disk (another calculus problem). Then, take the limit as r approaches infinity and compare the result with the electric field equation for a point charge.

    Hope that helps.
  4. Sep 4, 2004 #3
    Thanks, I think I have something to turn in at the least now. :p
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook