1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: EMF/ circuit question

  1. Mar 9, 2010 #1
    1. The problem statement, all variables and given/known data
    If R1 = 4 x R2 then what are the values of the potential difference in terms of the EMF, E?
    s.png
    I have R1 = 3/4, and R2 = 1/4 but that seems a bit simplistic, then I tried plugging it into equations and got completely different answers.

    2. Relevant equations
    R=V/I (?)
    EMF=v1 +v2


    3. The attempt at a solution
    First I simply put it as 1/4 and 3/4, then I plugged it into the equations:
    v=IR
    v1=1(4) =4
    v2=1(1) =1
    EMF=v1 + v2 = 5
    R2 = 1.25, R1 = 5

    ??
     
  2. jcsd
  3. Mar 9, 2010 #2

    collinsmark

    User Avatar
    Homework Helper
    Gold Member

    Solve the current, I. Express this interim result as a function of E, R1 and R2.

    Since you know that R1 = 4 x R2, you can now express the current solely as function of E and R2 (since R1 goes away after the substitution).

    Now that you know the current, using V = IR, find the EMF (i.e. voltage) across R2. You should be able to express it solely as a function of E (after some algebraic simplification).
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook