How to find voltage drop across each resistor in a complex circuit?

Question

I don't know how to find the voltage drop across each resistor in this circuit:

http://i229.photobucket.com/albums/ee8/flaviozelenka/circuit.jpg

Answer 1

Hey why not apply loop equations or Nodal equations on it. It Is pretty easy that way.

Try assuming two loops, assume the current i1 flows in the first and i2 in the second.

Write down Kirchoffs Voltage Equations for both the loops. You ll get 2 equations involving i1 and i2, solve them simultaneously and you have the actual values of i1 and i2, multiply them by their respective resistances and you ll get the voltage drops.

Remember that in r3, the sum or difference of i1 and i2 flow, depending upon the direction of i1 and i2 that you assume.

Answer 2

Kirchhoff's Voltage Law (KVL) states that the voltages around a closed loop must add up to 0.

Your calculation is correct.  All of the voltage drops add up to 20.58V.  But this calculation is meaningless.

Remember you cannot get more out of a circuit than you put in.  So you cannot just add the voltages of a complete circuit.

Look at your loops.  The voltage drop across R_3 is shared with both loops.  

KVL Loop 1: +12V - 9.41V - 2.59V = 0

KVL Loop 2: +6V - 8.58V + 2.59V = 0

Have fun...

edit...

OK, I'm confused.

The voltage across R_1, V_R1 is 9.41V.

V_R2 = 8.58V

V_R3 = 2.59V