1. Not finding help here? Sign up for a free 30min 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!

Parallel plates & Point charge ?

  1. Feb 28, 2005 #1
    1. parallel plate with capacitor of 20uF, plate is 0.5mm apart.

    Find
    1. Area of each plate
    2. potential difference if there's a change of magnitude of 30uC on each plate.
    3. stored energy
    4. electric field between the two plates
    5. charge density on the plate.


    |_| |_|
    |_____|
    .5mm

    I know [tex]C=\frac{Eo*A}{d}[/tex]

    so would [tex]A=\frac{Eo*C}{D}[/tex] or A=Q / Eo *E

    A= (8.85*10^ -12 ) * 20 / (.5 * 10^ -3) = 3.54 * 10 ^7 ?


    2. three point charges on the x axis q1= (10uc) at x= -4m, q2= (-5uC) at the origin, q3= (-20uC) at x= 4m.


    Q1(-4,0)...... Q2(0,0)...... Q3(4,0)
    (+)----------(-)-----------(-)
    10uC........ -5uC........ -20UC


    Find
    1. electric field at origin
    2. force on q2


    would electric field on orgin = Zero & force on q2 equal

    [tex]F1= Ke\frac{q1|q2|}{r^2}[/tex] , [tex]F2=Ke\frac{|q3|q2|}{r^2}[/tex]

    [tex]F1=\frac{(8.99* 10^9)* (10 * 10^ -6)*( 5*10^-6)}{(-4)^ 2}[/tex]

    [tex]F2=\frac{(8.99* 10^9)* (20 * 10^ -6)*(5*10^-6)}{(4)^ 2}[/tex]

    After this would i add components ( x i + y j )
     
  2. jcsd
  3. Feb 28, 2005 #2

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    For the first problem,the area u computed is incorrect.You began with the correct formula,but somehow screwed up the arithmetics.What about the other 4 points...?

    Daniel.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?