D.C circuits PLEASE help are my answers correct?

  1. 1. The problem statement, all variables and given/known data
    To find the emf and internal resistance of an unmarked battery you are given two resistor of value 5.0(ohms) and an ammeter. When the resistors are connected in parallel the current drawn from the battery is 2.0A. What are the e.m.f and internal resistance of the battery?

    Am i going right?
    2. Relevant equations
    E = IR = Ir

    3. The attempt at a solution
    Series
    R = 5(ohms) + 5(ohms) = 10(ohms)

    Parellel
    1/R = 1/5 + 1/5 = 2/5
    R = 2.5(ohms)

    E = 0.75*10 + o.75*r
    E = 7.5 + 0.75r ------- (1)

    E = 2*2.5 + 2r
    E = 5 + 2r ---------- (2)

    7.5 + 0.75r = 5 +2r
    2.5 = 1.25r
    2(ohms) = r

    there for r in equation 1 gives
    E = 7.5 + 0.75(2)
    = 9V
     
  2. jcsd
  3. ***TYPO****-*********Relavant Equation should be E = IR + Ir*******
     
  4. berkeman

    Staff: Mentor

    You didn't include the series combination part in your problem statement. But looking at your work, it would appear that you get 750mA when you connect them in series?

    If so, then the rest looks correct.
     
Know someone interested in this topic? Share this thead via email, Google+, Twitter, or Facebook

Have something to add?