Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: How do I calculate the power?

  1. Nov 7, 2007 #1
    1. The problem statement, all variables and given/known data
    We used a watt-hour meter in a lab, 400 revolutions of the dial = 1kWh. We measured the time for 10 revolutions of the dial ( in seconds).
    How would I calculate the power?

    Time for 10 revs = 146s

    2. Relevant equations



    3. The attempt at a solution
    Power = (3600s/hr) / (146s) * (10/400) *1kWh = 0.62069 W ?
     
    Last edited: Nov 7, 2007
  2. jcsd
  3. Nov 7, 2007 #2

    Astronuc

    User Avatar
    Staff Emeritus
    Science Advisor

    Does one mean Time for 10 revs = 146s or 146 revs in 10 s?
     
  4. Nov 7, 2007 #3
    Sorry... fixed :)
     
  5. Nov 7, 2007 #4
    ... After some more thinking...I think it should be 0.62069 kW. Would this be correct?
     
  6. Nov 7, 2007 #5
    Any help would be very much appreciated... :)
     
  7. Nov 7, 2007 #6

    Astronuc

    User Avatar
    Staff Emeritus
    Science Advisor

    Yes, but I calculate 0.6164 kW.

    Take (1 kWh)/(400 revs)*(10 revs/ 146 s) * 3600 s/h = ______ kW.

    The unit kWh is simply power (kW) * time (hours) = energy. 1 kW-s = 1 kJ, so 1 kWh = 3600 kJ.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook