Results 1 to 3 of 3

Math Help - 2 physic excercises

  1. #1
    Member
    Joined
    Jul 2005
    Posts
    187

    2 physic excercises

    First of all. I would not ask it if I had not missed consultation class today. Unfortunately I was late about 15 minutes and when I reached the class, the professor had left.

    1) Charge of 30 nanoCulomb is at the center of the sphere. The radius of sphere is 10 cm. Electric field strength 20 cm from center is 1500 V/m and it is pointing away from center. What is charge of the net ?
    I found that example http://physics.bu.edu/~duffy/semeste...rge_shell.html but it does not seem to be suitable for my case because I don't have a hollow sphere.

    2) Between a capacitor plates flies an electron parallel to the plates. Speed of electron is 10 000 km/s. The distance between two parallel plates is 2,0 cm and length of the plates is 5 cm. The voltage of the capacitor is 30 V.
    What is the speed of the electron at that moment when electron comes out from two prallel plates ?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Jul 2005
    Posts
    187
    Ok, I figured out the solution of the second excercise.
    I am still in need of help for the first excercise.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    10,211
    Thanks
    419
    Awards
    1
    Quote Originally Posted by totalnewbie View Post
    1) Charge of 30 nanoCulomb is at the center of the sphere. The radius of sphere is 10 cm. Electric field strength 20 cm from center is 1500 V/m and it is pointing away from center. What is charge of the net ?
    I found that example http://physics.bu.edu/~duffy/semester2/c06_pointcharge_shell.html but it does not seem to be suitable for my case because I don't have a hollow sphere.
    It doesn't matter whether the sphere is hollow or not: this follows from Gauss' Law for Electrostatics.

    You want the net charge inside a spherical Gaussian surface that encloses the entire sphere. You know that E is 1500 V/m a distance of 0.20 m from the center of the sphere. Since we are given only a radial distance from the center I am assuming that this E value holds for all positions on the Gaussian surface. So:
    EA = q(enc)/epsilon0

    q(enc) = (epsilon0)EA = (epsilon0)E(4*pi*R^2)
    where R = 0.20 m is the radius of the Gaussian surface.

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Review Excercises(Prerequisites for Calculus)
    Posted in the Calculus Forum
    Replies: 4
    Last Post: August 31st 2009, 08:51 PM
  2. basic physic formulae
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 27th 2009, 05:23 PM
  3. Some Algebra Excercises
    Posted in the Algebra Forum
    Replies: 0
    Last Post: October 5th 2008, 11:19 AM
  4. physic vector
    Posted in the Math Topics Forum
    Replies: 3
    Last Post: September 8th 2008, 12:16 PM
  5. Replies: 1
    Last Post: April 29th 2008, 08:23 AM

Search Tags


/mathhelpforum @mathhelpforum