Power loss

Discussion in 'Homework Help' started by kvi037, May 17, 2013.

  1. kvi037

    Thread Starter New Member

    May 17, 2013
    17
    0
    Hi,

    Can anybody help me with this problem?

    The voltage across the inductance and resistance in series LR circuit is
    v= 141,4 cos wt and the current through the resistive portion of the circuit is iR = 2,80 cos (wt-pi/6). Calculate the power loss for the circuit.

    Correct answer should be 173 watts

    I appreciate it a lot if you can help me:)

    Thanks!
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    What working can you show thus far?
     
  3. kvi037

    Thread Starter New Member

    May 17, 2013
    17
    0
    Thanks for reply.

    I started to figure out Z by:
    Z= Û/Î*agle(-pi/6) = 100/1.97* angle (-pi/6) = 50.75 + j0.46

    P = i^2 *R = 1.97 ^2 A *50.75ohms = 198.4 W

    But this is not giving me the right answer. Do you have som suggestion for a better way to do it?
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Your Z value is wrong. Probably because you are using your calculator in degrees mode rather than radians mode. The angle ∏/6 is in radians.
     
    kvi037 likes this.
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