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: Current Density

  1. May 15, 2004 #1
    Let E=Eo (err...free space, not sure how to represent the symbols)
    V=90z^(4/3) in the region z=0(Potential)
    a) Find expressions for E,D and pv (volume charge density) as functions of z

    My work:
    E=-div V=0+0)120z^(1/3)az=120z^(1/3)az V/m
    D=Eo E=1.062z^(1/3)az nC/m^2
    pv=div D=.354/z^(2/3) nC/m^3

    b)If the velocity of the charge density is given as vx=5x10^6 *z^(2/3) m/s, find Jz (current density) at z=0 and z=.1m

    My work:
    Now this is where I am confused because J=pv*v (volume charge density*velocity vector). And the book only gives the x component of the velocity vector and asks for the z component of the current density. If you ask me, that means the z component of the current density is 0, but I have no way of checking my answer.

    :confused:

    Is this correct?
     
    Last edited: May 16, 2004
  2. jcsd
  3. May 16, 2004 #2
    Still not sure about part b of this one, and running into more problems with the stuff :cry:
     
  4. May 18, 2004 #3
    Teacher posted solutions today....

    had Jz=Pv*Vx ...

    Still don't believe that though unless it was a misprint in the book or something ... doesn't make sense to me
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook