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HW about physics, electircal engineering. Help please

  1. Mar 19, 2014 #1
    1. The problem statement, all variables and given/known data

    Hi! My lecturer has given a HW qustion which is as follows:

    Can you find a set of charges that are stable? ( total electrical force will be zero)

    note: neutral charge is forbidden


    2. Relevant equations
    F=k..q1.q2/d^2


    3. The attempt at a solution

    I drew some shapes for neutral electrical force but cannot prove as mathamatical equation

    . Shape can be drawn as a square whose one corner is near to the center with respect to other corners, which becomes not a ordnary square by the way
     
  2. jcsd
  3. Mar 19, 2014 #2

    rude man

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    Gold Member

    what are the polarities of your 4 charges? Did I get that right - 4 charges?
     
  4. Mar 19, 2014 #3

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    Is that the full problem statement? Do they mean the electric force on *one* charge when placed in a group of other charges? Or do the forces on *all* of the charges need to be zero?
     
  5. Mar 19, 2014 #4
    The force exerted on each charge will be zero. There is no mentioned about type of charges but you cannot use neutral charge. It is full problem statement. Actually it is conceptual problem. You will decide how many charges you will and their locations.
     
  6. Mar 19, 2014 #5

    berkeman

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    Fair enough. Use the force equation and maybe induction to prove whichever viewpoint you think is correct...
     
  7. Mar 19, 2014 #6

    berkeman

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    Actually, I initially thought that it would not be possible, but I think there may be at least one configuration that could work. I need to sketch it up to see if it could work.

    I'd suggest starting with a 1-dimensional geometry to see if you can find a way to balance electrostatic forces...
     
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