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Homework Help: Net force on charges found to be zero

  1. Sep 3, 2006 #1
    I'm having trouble understanding some of these basic electrostatic priciples and my book isn't much help. I've put them in a true/false format. If I could get at few answers, it would really help me understand this.

    A positive point charge +q is placed at point p to the right of two charges, A and B. The net force on the +q charge is found to be zero. Which of the statements below are true?


    True or False -- The magnitude of the charge A must be smaller than B.

    True or False -- Reversing the sign of +q to -q would make the force on it nonzero.

    True or False -- B must have the same sign as A and be less in magnitude.

    True or False -- B must have the opposite sign from A and be less in magnitude.

    True or False -- Either A or B must be positive.
  2. jcsd
  3. Sep 3, 2006 #2
    Welcome to PF eltel.
    What are your thoughts on how to go about solving the questions ?
    Start from the basics, namely Coulomb's law .
  4. Sep 3, 2006 #3
    I eltel,
    you must analyse two cases:
    A negative then B must be positive so that the net force be zero on p.
    A positive then B must be negative....
    Then use Coulomb's law to complete your reasoning.
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