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: EMF and circuits

  1. Feb 24, 2008 #1
    1. The problem statement, all variables and given/known data

    The voltmeter is removed (previous question was a voltmeter connected to a battery and it reads 12 V) and a resistor of 21 ohm is connected to the battery. What is the current (I) through the battery?


    2. Relevant equations

    emf=V
    I=emf/(R+r)

    3. The attempt at a solution

    I tried to do I=12V/21 ohm but I don't know how to find R. When I entered the solution of that, it said to include the internal resistance of the battery, but I don't know the current of the battery so I can't use emf=IR to find R.
     
  2. jcsd
  3. Feb 24, 2008 #2
    Is there an answer in the back of the book to compare to?
     
  4. Feb 24, 2008 #3
    haha nevermind. I was having trouble because I didn't have enough information, but I just didn't see where it was written. Thanks for your help anyway!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook