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!

3 excess electrons calculate the radius

  1. Feb 18, 2010 #1
    3 excess electrons...calculate the radius...coaxial cable...

    1. The problem statement, all variables and given/known data
    An oil droplet with 3 excess electrons is held stationary in a field of 4.24x104N/C.
    What is the radius of the oil drop?( The density of the oil is 824 kg/m3,e=1.60x10-19C)

    2. Relevant equations

    3. The attempt at a solution
    well i assumed that the droplet was a sphere and so the volume would be (4/3 [tex]\pi[/tex]r3. So i set F=qe=mg because the droplet is stationary so the net force is zero. And the mass = density x volume so i just plugged every thing in and solved for r ...i got 8.43 x 10-7....can some one verify this ..i am not really confident lol

    1. The problem statement, all variables and given/known data
    The cross section of a long coaxial cable is shown, with radii as given. The linear charge density on the inner conductor is-10nC/m and the linear charge density on the outer is -40nC/m. The inner and outer cylindrical surfaces are respectively denoted A,B,C and,D ad shown. The linear charge densities on surfaces C and D, in nC/m, are closest to:
    A) +10 and -40
    B) -10 and -30
    C) 0 and -40
    D) +10 and -50
    E) -30 and -10


    2. Relevant equations
    I'm not exactly sure what to do...
    3. The attempt at a solution
    The only thing i could think of was that the system is a conductor so the inside charges must be equal to zero and so i thought that what ever the inside charges added up to then the outside charge would be the same magnitude as the sum of the inside charges but opposite in sign. I don;t even know if that is conceptually correct ...please help ...i don;t think i understand the underlying concept of this question...let alone actually solving it haha.
    Last edited: Feb 18, 2010
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted

Similar Threads - excess electrons calculate Date
Charge and excess electrons Jan 26, 2017
Excess Electrons, Milikan Oil Drop Mar 15, 2014
Excess or deficit electrons. Oct 28, 2013
How many excess electrons? Sep 1, 2013
Calculate the number of excess electrons Mar 21, 2007