Kirchhoff's Loop Rule

Kirchhoff's loop rule states that the algebraic sum of the changes in potential around any closed loop of a circuit is zero, and this is a direct statement of energy conservation, as explained in NCERT Class 12, Chapter 3 (Current Electricity). A unit charge carried once around a complete loop returns to its starting potential, so the energy it gains from sources must equal the energy it loses across resistors. Mathematically, $\sum \epsilon =\sum IR$ around the loop. The option about charge conservation at a junction describes Kirchhoff's other rule, the junction rule, which balances currents rather than potentials and is a separate law. The option about electron momentum is irrelevant, since the loop rule concerns electric potential energy per unit charge, not the mechanical momentum of individual carriers. The option about magnetic flux belongs to electromagnetic induction and Faraday's law, which governs changing fields, not steady resistive direct-current circuits. A plausibility check reinforces the idea: electric potential is a single-valued function of position, so returning a test charge to the very same node must return it to the same potential, forcing the net algebraic change around any closed loop to vanish exactly as the rule requires.