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: Electric Circuits EMF

  1. Oct 30, 2007 #1
    1. The problem statement, all variables and given/known data

    You'll have to forgive me... I've got some rather poor Physics books with which to consult, so this may seem rather simple. I think I understand the concepts but I don't think I have all of the information from my sources to answer this problem.

    A 1.5 V battery stores 4.3 kJ of energy. How long can it light a flashlight bulb that draws 0.6A?

    Units should be in hours, but I'm not sure what to do with only having equations V = IR and I = E/R (where E is epsilon, of course). I don't know what part of this factors into time!!!
     
  2. jcsd
  3. Oct 30, 2007 #2

    Kurdt

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The electric power in a DC circuit is [itex] P =IV [/itex]. Is that enough to get you going?
     
  4. Oct 30, 2007 #3
    Guess it'll have to be. Thanks.
     
  5. Oct 30, 2007 #4

    Kurdt

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If you have more questions I'll be happy to clarify :smile:

    The units of power are of course Joules/second. That is where the time comes into it.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook