The question involves deriving three equations using Kirchhoff\'s junction and l

Question

The question involves deriving three equations using Kirchhoff's junction and loop rules. I had no problem deriving the equations (the actual PHYSICS part of the question), but my algebra is not yielding the same results as the book.

Using the junction rule, I got the first equation: I1 - I2 - I3 = 0 (where I is current).

Using the loop rules, I got the other two equations: 15V - I3R - I1 R = 0 and -9.0V - I2R + I3R = 0. R is equal to 100 ohms in each equation. Using these three equations, we're asked to find I1, I2, and I3 (the three currents).

The answers given by the book are I1 = 0.070 A, I2 = -0.010 A, and I3 = 0.080 A. If somebody could show me the steps of algebra leading to these answers, I would really appreciate it!! Thanks guys.

Explanation / Answer

start with 15 - I3*100 - I1 * 100 = 0 add I1 *100 to both sides 15 - 100*I3 = 100*I1 divide by 100 I1 = .15 - I3 now go to other equation -9 - 100I2 + 100I3 = 0 add 100I2 to both sides -9 + 100 I3 = 100 I2 divide by 100 -0.09 + I3 = I2 plug both of these into I1 - I2 - I3 = 0 .15 - I3 +0.09 - I3 - I3 = 0 .24 = 3 I3 I3 = 0.08 take this and plug it back into previous equations I1 = 0.07 I2 = -0.01

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