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Homework Help: Electric Field, Excess Charge Conceptual Question

  1. Sep 8, 2012 #1
    1. The problem statement, all variables and given/known data

    1. A balloon is charged with excess charge. This balloon is then put in a space with a
    uniform electric field pointing towards +x direction. When there is no wind around,
    this balloon is observed moving towards the -x
    direction. What is the sign of excess
    charge on the balloon?

    (A ) Positive.
    (B ) Negative.
    (C ) Not enough information.
    (D) Neutral.

    2. Relevant equations


    3. The attempt at a solution

    I thought the answer was "A" but that is incorrect. I thought so only because of the second to last sentence. I thought of the whole "opposite charges attract." I also don't understand the significance of saying which direction the electric field is in, only that it points from positive to negative.
  2. jcsd
  3. Sep 8, 2012 #2


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    Homework Helper

    It is assumed that the electric field is originated from positive charge and radiates away from that. If a positive charge is placed in the electric field, it moves in the direction of the elelctric field due to the repulsion. If the negative charge is placed in the elelctric field what happens?
  4. Sep 8, 2012 #3
    If a negative charge is placed instead it would move in the opposite direction of the electric field. Electric field lines, however, originate from positive charges to negative charges. I think I was mixing those two concepts.
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