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Homework Help: Circuit resistance problem

  1. Mar 7, 2013 #1
    1. The problem statement, all variables and given/known data

    https://www.dropbox.com/s/8tbqxmeoiulxg7s/Screen shot 2013-03-06 at 7.54.11 PM.png

    The three light bulbs A, B, and C do not necessarily have the same resistance. The battery voltage remains constant. Click on a wire to cut that will result in the light bulb C glowing brighter. If it is not possible to do this, click in the target area. Careful, you get only 3 clicks.

    Hint: Write out the formula for the current through the bulb and see what happens if one of the resistances goes to infinity. Use the methods found on the pages for parallel and series resistors.

    2. Relevant equations

    Resistors in series (Req = R1 + R2 + ...)
    Resistors in parallel (1/Req = 1/R1 + 1/R2 + ...)

    3. The attempt at a solution

    On the picture you can see that there is a "x" on the wire between bulbs B and C. That is where I thought the wire had to be cut since this would remove resistors A and B, but it was wrong. I think it may be impossible to do this, but I only have two attempts left so I want to make sure I do not make a mistake again.

    Thank you!
    Last edited by a moderator: Mar 7, 2013
  2. jcsd
  3. Mar 7, 2013 #2
    If you cut at that point then the circuit won't be closed so there won't be any current.
    Last edited: Mar 7, 2013
  4. Mar 7, 2013 #3
    I think the answer is impossible. c is the only one that can be cut out but if you were to cut it out it would increase the resistance of b. This is because the equivalent resistance of two parallel resistors is less then the resistance of the resistors.
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