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[Circuits] Calculating the power absorbed by a resistor

  1. Jan 20, 2014 #1
    1. The problem statement, all variables and given/known data

    yAw0XtS.png

    2. Relevant equations



    3. The attempt at a solution

    Attached to this post.

    I have calculated the power absorbed for the 6S and 5S resistors but not the 3S resistor.
     

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  2. jcsd
  3. Jan 20, 2014 #2

    gneill

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    Staff: Mentor

    Your values look okay for the 6S and 5S resistors. Why didn't you calculate the power absorbed by the 3S resistor?
     
  4. Jan 20, 2014 #3
    Here is my attempt for the 3S resistor:

    $$R=\frac { V }{ I } \\ \frac { 1 }{ 3 } =\frac { V }{ 6 } \\ V=2\quad V\\ \\ P=VI\\ P=2\cdot 16\\ P=32\quad W$$
     
  5. Jan 20, 2014 #4

    gneill

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    Where did you get 16 A from for your P = VI calculation? You used I = 6 A in the second line.

    Note that while power is indeed given by P = VI, for a resistor it's also given by V2/R and I2R, so you can avoid some steps if you already have either V or I.
     
  6. Jan 20, 2014 #5
    So P=12W?
     
  7. Jan 20, 2014 #6

    gneill

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    Is that a guess or a conclusion?
     
  8. Jan 20, 2014 #7
    Conclusion.

    I used 16 A by accident. Not sure where I got the 1 from.
     
  9. Jan 20, 2014 #8

    gneill

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    Okay, so it looks like you're done :approve:
     
  10. Jan 23, 2014 #9
    IMG_1516.jpg
    You got right.
     
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