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Homework Help: Electric Field

  1. Jul 11, 2010 #1
    1. The problem statement, all variables and given/known data

    Two point charges, -30 and +50 , are separated by a distance of 17.0 cm . (micro couloumbs)

    Express your answer to two significant figures and include the appropriate units.

    2. Relevant equations


    3. The attempt at a solution
    E1=9E9*30E-6/.085^2= 3.73*10^7
    same for E2 =6.23*10^7
    E2-E1=2.5E7 N/C
    Really not sure on how to do this, i was just doing what seemed logical to me but the procedure could be entirely wrong. ( I am sure that my answer is wrong)
  2. jcsd
  3. Jul 11, 2010 #2


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    Homework Helper

    If you are finding the net field at the center of the line joining the charges, then the electric fields at the center are in the same direction. So the net field at that point is E = E1 + E2.
  4. Jul 11, 2010 #3
    thanks, i now have the correct answer but part to of the question is What is the direction of the electric field at a point halfway between the two charges?

    I think that it would be toward the positive charge since it is bigger??????
  5. Jul 11, 2010 #4
    E is defined as the force acting on unit positive charge.
  6. Jul 11, 2010 #5
    so it would actually be toward the negative charge since the positive charge would repel it???
  7. Jul 11, 2010 #6
  8. Jul 11, 2010 #7
    thanks dadface
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