How do we know that Phi1 is points at of F N1 i1 and not po

How do we know that Phi_1 is points at of F = N_1 i_1 and not points down into F? How does KCL say Phi_1 = 0? What is the reasoning? Also why does Phi_2 point into F.

Solution

1)

current always flows out of the positive terminal from voltage source always, so obviously respected current leaves out of the positive terminal.

2)

consider ground at node of R1 and R2 , thus that node joining to the R3 is also ground point which implies current flows between them is zero.

and as for the ideal source current is always flows into the voltage source thats why PHI2 is pointing into the source