1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Need help with unit conversions!

  1. Jul 17, 2009 #1
    1. The problem statement, all variables and given/known data
    A steam iron draws 5.3 A from a 114 V line. (a) How much internal energy is produced in 76 minutes? Answer in J. (b) How much does it cost at $0.75/kW*hr to run the steam iron for 76 minutes? Answer in units of cents.


    2. Relevant equations
    1) U = VIt


    3. The attempt at a solution
    Using equation 1, I found the internal energy produced to be 2755152 J. However, I'm having a problem with figuring out part (b). I know I'm supposed to convert J to kW*hr in order to figure out the cost and that 1 watt = 1 J/s. Using that information I divided the internal energy by the time, 4560 seconds, giving me 604.2 watts or 0.6042 kW. I then times that by the cost per kW/hr and the amount of time in hours. I got 0.57399, but for some reason it's not the right answer.
     
  2. jcsd
  3. Jul 17, 2009 #2

    rock.freak667

    User Avatar
    Homework Helper

    2755152 J =2755152 Ws

    Divide by 1000 to get it in kWs, then divide by 3600s to get it in kW*hr
     
  4. Jul 17, 2009 #3

    LowlyPion

    User Avatar
    Homework Helper

    Maybe enter it in cents?
     
  5. Jul 17, 2009 #4
    I tried that and I get the same exact answer that I got. I even tried putting it in as 0.57 but that was marked wrong as well...
     
  6. Jul 17, 2009 #5

    rock.freak667

    User Avatar
    Homework Helper

    Your answer is $0.57399, convert that into cents.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Need help with unit conversions!
  1. Unit conversions help (Replies: 1)

Loading...