Calculating power with a wattmeter

Discussion in 'Homework Help' started by nyasha, Oct 15, 2011.

  1. nyasha

    Thread Starter Active Member

    Mar 23, 2009
    90
    2
    I calculated the power for this circuit and got a positive value of 1100 watts. However in the textbook they have the solution being negative. Can someone please tell me why ?

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  2. #12

    Expert

    Nov 30, 2010
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    9,401
    One point of view is that a negative amount of power means the circuit is absorbing 1100 watts of heat from the surrounding air. This being impossible, I thing the book is wrong. Typographical error.
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    67
    The winding for measuring the voltage (bottom one) has its dot to the right. This means that it measures a negative voltage (or 180 degrees phase shifted) which gives a negative power.
     
  4. #12

    Expert

    Nov 30, 2010
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    9,401
    I wish my electric company believed that!
     
  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,710
    1,570
    Doesn't matter. They would use abs(#12's power meter) to compensate for the "negative power". :)
     
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