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Homework Help: Help finding battery voltage.

  1. Sep 17, 2008 #1

    crh

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    1. The problem statement, all variables and given/known data

    In the circuit shown, the 33-ohm resistor dissipates 0.50 W. What is the battery voltage?

    http://phga.pearsoncmg.com/phga2/web/Giancoli6e/Public_Html/Chapter19/Aadxevw0.gif

    2. Relevant equations

    I am pretty sure that I use the equation V=IR, but I am not for sure how to go about using the 0.50W in the equation. At first I thought that I used P=IV for electric power, but I am just confused.

    3. The attempt at a solution

    I don't even know what equation to exactly use because the watts are throwing me off.
     
    Last edited by a moderator: Apr 23, 2017
  2. jcsd
  3. Sep 17, 2008 #2

    LowlyPion

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    Homework Helper

    You should know from Watts = V*I and V= I*R that Watts = I2R
    Watts is your equation for P = Power.

    So knowing the watts of a resistor lets you figure out the current.

    Knowing the current and figuring the equivalent resistance for the 3 resistors through the V=I*R tells you the voltage of the supply.
     
    Last edited by a moderator: Apr 23, 2017
  4. Sep 17, 2008 #3

    crh

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    thank you, I figured it out with your help.
     
  5. Sep 17, 2008 #4

    LowlyPion

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    Homework Helper

    Good luck then.
     
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