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 and distance

  1. Jan 11, 2016 #1
    1. The problem statement, all variables and given/known data
    https://s.yimg.com/hd/answers/i/c7a04ad5e8d74b57a246295c815e183d_A.jpeg?a=answers&mr=0&x=1452518295&s=c54275383477f3e40a56996127dfee96 [Broken]

    2. Relevant equations
    Electric field, electrostatic
    3. The attempt at a solution

    E=v/d
    d=100/800
    d=0.125m

    V=Ed
    =800(0.125+0.4)
    =420V
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Jan 11, 2016 #2

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    That one is correct.
    By potential at X, the question must refer to the potential difference between point X and the 0 V. So, 0.125+0.4 is not the correct value for the corresponding distance.
     
  4. Jan 11, 2016 #3
    that mean ed = 800x0.40 only?
     
  5. Jan 11, 2016 #4

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    Yes. Just, be careful with the proper sign of the potential.
     
  6. Jan 11, 2016 #5
    https://scontent-hkg3-1.xx.fbcdn.net/hphotos-xfp1/v/t1.0-9/12509720_10205411857847476_602511770052026952_n.jpg?oh=66b58b8024f86e46c7a9c860c4d89bcf&oe=56FB9605

    neeed help about 15b.
    W= kq/r + kq/r ?
    no idea about it.hehe
     
  7. Jan 11, 2016 #6

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    Just want to remind you, in case you are not yet aware of, that that answer is still missing something to be justified according to the physical situation given in the problem.
    Write down the formula of electric field due to each charge along the connecting line, define this line as ##x##. Denote ##x_1## and ##x_2## as the distances of a given point from ##Q_1## and ##Q_2##, respectively. The equation you have there is wrong.
     
  8. Jan 11, 2016 #7
    Whats the missing part actually? i got 320 V. I am not sure it is -320 or +320V actually. but i guess it should be -320 since V is decreasing.

    Q1= k(40uC)/12cm
    Q2 =k(80uC)/12cm thats the only thing i can think about it.
     
  9. Jan 11, 2016 #8

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    Yes, it should be -320, otherwise the E field vector cannot be uniform everywhere.
    No, that's still not correct. Please look up "Coulomb's law" either in your book or in the internet.
     
  10. Jan 11, 2016 #9
    Perhaps it should be kqq/r
    can u explain this concept to me? i thought product of charges over distance is only used to determine the force, never thought u can be express as electric potential too.
     
  11. Jan 11, 2016 #10

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    There is no "perhaps" in this matter because the related equation which is sometimes called "Coulomb's law" had been agreed upon among the physicists long time ago. You will gain much more knowledge by searching/reading on your own about this basic concept of electric field by a point charge in electrostatics than you will if someone were to explain that to you.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Electric Field and distance
  1. Electric Field distance (Replies: 16)

Loading...