Solve the circuit using nodal analysis and find the power of .

**Solution**

a) Choose a reference node, label the voltages:

b) Apply KCL to nodes:

Node #1:

Node #2:

Node #3:

.

c) Find the unknown:

supplying.

Solve the circuit using nodal analysis and find the power of .

**Solution**

a) Choose a reference node, label the voltages:

b) Apply KCL to nodes:

Node #1:

Node #2:

Node #3:

.

c) Find the unknown:

supplying.

Can we ignore R2-Is2 loop and say that R1 and R3 are in series so R13=5ohm and the power is RI^2=5*2^2=20W?

Yes, it is ok to ignore the $latex R_2$ – $latex Is_2$ loop because it has only one common point with the other loop and current cannot flow between. Your solution is also correct.

I got 20W for the answer. How do you know if it is negative or positive? I know SRS, however I am not sure of how to apply it in this problem. Where do the plus and minus go?