Please suggest what does N1 and N2 mean in the attached dc network.
As far as I can tell, it is utterly meaningless without further information.
I believe they simply denote nodes. Apply KCL to them.
That makes no sense. They have different currents going in/out but nothing to show how that affects the rest of the circuit.
The problem is essentially indicating that if the upper and lower corners of the bridge are shorted, we will get 1A flowing from the upper to the lower corner. This is possible since the bridge includes a power source. Just apply KCL to each of the nodes, N1 must have 1A arriving from bridge, N2 must have 1A returning to bridge.
You know what, this does make no sense. If it is assuming a short between upper and lower corners, then the voltage in question would be zero.
If we assume that the voltage is non-zero, and we can see that there is 1A of external current associated with it, this means that the bridge is resistively loaded. But there is no resistor external to the bridge shown, only node numbers.
I'm flummoxed, too.
How about: N1 and N2 represent supernodes; we don't know what's inside each, but they are independent networks with three outside connections each. The currents between the two are shown, leaving us to deduce the remaining currents...
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