Kirchhoff's circuit laws

  • Thread starter Bob Loblaw
  • Start date
  • #1
69
0

Homework Statement



http://img207.imageshack.us/img207/1685/p1854altco4.gif [Broken]

Find the unknown emf and the unknown currents in the circuit below, in which R = 3.48 . Take the positive direction for current flow in each branch to be upwards.
EMF = V
left branch= A
right branch= A


Homework Equations



Kirchhoff's circuit laws

The Attempt at a Solution



I added current lines to the diagram. Note that a coordinate system is imposed and all positive charges point up ( I guess this makes grading easier). I sketched the lines of current as best I could.

Here are my equations:

Left loop:

1.00v-3.48I1-E+(.05*2)

Outside loop:

1.00v-3.48I1-1.00I3+1.20V+4.00I3=0 (edit: caught a mistake here, last term should have been positive)

Apply junction rule to top center junction:
I1+.05=I3

Combine terms:
1.00v-3.48I1-E+.1=0
2.20v-3.48I1+3.00I3=0

Substituting I1+.05 for I3:

2.20v-3.48I1+3.00I1+.15=0

Combining like terms:

2.35-.48I1=0

I1(the left loop)=4.90A which is wrong.

Any ideas where I messed up?
 
Last edited by a moderator:

Answers and Replies

  • #2
Where is the circuit diagram???????????????
 
  • #3
69
0
Where is the circuit diagram???????????????

Blast from the past! I have since moved past physics and on to medicine so things worked out well enough I suppose.
 

Related Threads on Kirchhoff's circuit laws

  • Last Post
Replies
11
Views
949
  • Last Post
Replies
10
Views
1K
  • Last Post
Replies
14
Views
2K
  • Last Post
Replies
8
Views
959
Replies
4
Views
889
Replies
6
Views
274
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
976
  • Last Post
Replies
2
Views
383
Replies
11
Views
17K
Top