Use the node-voltage method to find how much power the current source extracts from the circuit if i=7.8 A and v = 35 V. Answer in watts.?

Parallel combo of r's is 4.545ohms
I(v)=-6.455A.  V(50)=67.273v
P(i)=67.273v*7.8A=524.7W

Circuit simulator applet ...Show more

This ckt only has one "Node" above the 50Ω since the 1Ω and 4Ω are in series.
Let the bottom left of the ckt = ground and above the 50Ω be node V1
KCL at V1:
-7.8 + V1/50 + (V1-35)/5 = 0    Multiply eq. by 50
-390 + V1 + 10V1 - 350 = 0
11V1 = 350+390 = 740  so V1 = 750/11
The current source delivers 740/11 * 7.8 = 5772/11 W = 524.73W
The voltage source consumes 35V * 355/55 A = 225.91W
The resistance consumes (74/55)²*50+(355/55)²*5 = 298.82W
Total consumed = 225.91+298.82 = 524.73W  Checks...Show more