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Homework Help: Question 3

  1. Feb 4, 2005 #1
    Question 4

    What is the charge q_1?

    What is the charge q_2?

    What is the charge q_3?

    Unsure of which equation to use, and the equations that I am looking at involve integration.

    Φ = integral (E * dA) = EA sphere

    Φ = q / ε

    Can someone teach me how to do this problem?
     

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    Last edited: Feb 4, 2005
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  3. Feb 4, 2005 #2

    dextercioby

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    HINT:Use the property of the electric flux (which is a scalar) of adding wrt the same surface.You'll have to solve a very simple system of equations...

    Daniel.
     
  4. Feb 4, 2005 #3
    Property of Electric Flux = EA cos theta? But there is no theta. Unsure of the area and of the E.
     
  5. Feb 4, 2005 #4

    dextercioby

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    No.Let be [itex] \Phi_{1} [/itex] the electric flux generated by a charge [itex] q_{1} [/itex] through the (closed) surface S.Similar [itex] \Phi_{2} [/itex] for q_{2} [/itex].Then the total flux is simply the sum of Phi's which,due to the same denominator (epsilon),translates to the charges...

    Daniel.
     
  6. Feb 4, 2005 #5
    So what is the charge of q_1, q_2, and q_3?

    -q/E + (-2q/E) + 3q/E = 0/E = 0

    The charge of each is 0?
     
  7. Feb 4, 2005 #6

    dextercioby

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    No,you have to write equations of the type phi_{1}+phi_{2}=phi_{tot} for all 3 surfaces & will end up with an algebraic system of 3 eqn. with 3 unknowns,namely the charges.

    Daniel.
     
  8. Feb 4, 2005 #7
    Okay, got it. The answers are 2q, q, -3q. Am I correct?
     
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