(3 38) between the positive terminal P and the negative terminal N; I
here is the current flowing from N to P through the cell] If, while labelling
the current I through the cell one goes from P to N, then of course
V = e + I r
(3 60)
(a)Having clarified labelling, we now state the rules and the proof:
Junction rule: At any junction, the sum of the currents entering
the junction is equal to the sum of currents leaving the junction
(Fig