# KCL and simultaneus eqs.

1. Jun 4, 2009

### tommoturbo

1. The problem statement, all variables and given/known data

I am struggling as usual with quite a confusing circuit i need to find i1 i2 and i3 in this circuit using kirchoffs laws

i know i need 3 loops

loop 1 is V1...ABCD....V1

loop 2 is V1...ACD.....V1

Loop 3 is V1....ABD....V1

2. Relevant equations

R1=.5 ohm R2=1 ohm R3=1ohm R4=.5ohm R5=1ohm

3. The attempt at a solution
i have worked out loop1 to be

I1R1-I3R5-(I2+I3)R4 = 1V

but the other loops look wrong and then i cant seem to use simultaneus equations effectively.

Any help much appreciated

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2. Jun 4, 2009

### The Electrician

I can't view your image until it's approved. If you'll upload it to a free image hosting site, and post the link here, I'll be able to view it sooner.

3. Jun 4, 2009

4. Jun 4, 2009

### The Electrician

The currents you've shown are branch currents, not loop currents.

The circuit is an unbalanced wheatstone bridge. See:

http://en.wikipedia.org/wiki/Wheatstone_bridge

If you redraw it to look like a wheatstone bridger, it will be easier to draw distinct loop currents.

5. Jun 4, 2009

### tommoturbo

Hi Electrician

Thats how i initially approached the question i sent my workings out to my tutor who told me to seperate it into the three loops and then use simultaneus equations to find the unknowns,

when i did it initially whith the wheatsone bridge approach i got values of 1.5 1 and 05 for the various currents when i do the loops the values in teh equations are mostly .5's and 1s
and are difficult to multiply out

6. Jun 4, 2009

### The Electrician

Post a new image with the circuit drawn as a wheatstone bridge with 3 loop currents indicated. Show the equations you derived for each loop. Then I can help you.

7. Jun 5, 2009

ok will do!

thanks Ian