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!

Electric Field charge calculation

  1. Sep 3, 2005 #1
    Hi

    This is a homework question, but Im trying to see if Ive got the format correct. Two protons are separated by 3.80 x 10-10m. Find the electric force exerted by one proton on the other

    ........................... |q1||q2|
    So Ive got Fe =.. ke ------------
    ............................... r^2

    Im told the proton charge is +1.6021917 x 10-19

    so................... 2.5667E-38
    ............ke * .. -------------
    ...................... 1.444 E-19

    then...... ke * 1.7775 E -19

    then 1.5979 E-9 as the final answer?

    Is there some way to write equations and allow whitespace?
     
  2. jcsd
  3. Sep 4, 2005 #2
    [itex] F = \frac{2.5667E-19}{1.444E-19} [/itex]

    Okay I wrote this by typing this: [ itex ] F = \frac{2.5667E-19}{1.444E-19} [ /itex ] (take out the spaces in the tags with the square brackets.)

    [tex] F_{total} = K_e \frac{Q_1 Q_2}{r^2} [/tex]

    This was written with this:[ tex ] F_{total} = K_e \frac{Q_1 Q_2}{r^2} [ /tex ] (again take out the spaces)
     
    Last edited: Sep 4, 2005
  4. Sep 4, 2005 #3
    Hey thats too cool [itex]F_{total} = K_e \frac{q_1 q_2}{r^2}[/itex]

    its not working on preview, anyone know if the result is correct?

    also, would 15 pounds of electrons have enough field energy to support the mass of the earth? It calculates out to be many times more, but if thats the case? batteries can still be improved to store more energy

    This is my first Physics for electricity/Magnetism course
     
  5. Sep 4, 2005 #4
    Without doing any equations, I'm pretty sure 15 pounds of electrons would be more than enough to support the Earth. What you mean by support the earth though, I'm not sure. The electromagnetic force is some 38 orders of magnitude (or thereabouts) stronger than gravity. You would have some problems though:
    -How do you get 15 pounds of electrons without any protons
    -Given that the electromagnetic force is so strong, how do you contain them, since they will want to repulse each other.
    - The overall net charge on the earth (I'm assuming) is probably very close to zero, so the net force on the earth is going to be very small.
    But yeah, the electromagnetic force is much, much stronger than gravity, its just that in everyday life, almost everything has the same number of positive and negative charges, so it cancels out.
     
  6. Sep 4, 2005 #5
    One of our questions was 2 people standing at arms length, each has 1% excess in their body weight of electrons, would there be enough force between them to lift the mass of the earth? or something like that.

    I got the result down to Newtons, starting with each person 150lbs, oops I calculated 15lbs but thats 10%? 1.5lbs of excess electrons...

    And I figured the distance was 2 meters. taking the weight of electrons, dividing in 15 pounds, got some number then multiplied to get charge then applied the F_e equation with the distance as 2m and it came out to 3.23 E33 Newtons of force or 3.29 E32 kG of force and the earth weights a mere 6 E24 kG ?

    Yes, how to contain the charge. dont know... maybe need particles smaller than an electron that have even stronger bonds to make a container. Arent radioactive materials extra heavy because they have too many electrons? What would it take to order the electrons back to the nucleus?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?