Calculate Emf of Battery in Figure | Homework Problems and Solutions

[DrMcDreamy]

Homework Statement

What is the emf E of the battery at the lower left in the figure? Answer in units of V.


http://img508.imageshack.us/img508/6/82852928.png



Can someone guide me? I'm confused as to where to start. I think I am supposed go the route of the loop, but I am given the current as 3.54 A. How would I find the emf from there? TIA

 

[ideasrule]

Label all currents. Then, write out Kirchoff's current law for each junction, and Kirchoff's voltage law for each closed loop. That should give you the right number of equations to solve for the emf.

 

[DrMcDreamy]

So would it be:

\epsilon+(1.69x3.54)+(9.34x3.54)+(5.66x3.54)+(1.74x3.54)+11.88v=0
\epsilon=-77.44

 

[DrMcDreamy]

Okay, that's wrong, I only have one more chance to put in the correct answer, so how would I do this?

 

[gneill]

Write the loop equations for both loops. Watch out for the polarities of the voltage sources. You're given one loop current, so there are still just two unknowns: the second loop's current and the voltage supply value.