Kirchhoff's second law for an electric network is based on:

The correct answer is Option (3) → Law of conservation of energy

Kirchhoff's second law (loop rule) says that the algebraic sum of the changes in potential around any closed loop is zero.

Potential difference is energy per unit charge. A charge taken round a closed loop returns to its starting point with the same potential energy, so the energy gained from the cells equals the energy lost in the resistors. The loop rule is therefore based on conservation of energy.

Option (1) Law of conservation of mass — Incorrect. Mass plays no part in the circuit laws.

Option (2) Law of conservation of charge — Incorrect. Conservation of charge is the basis of Kirchhoff's first law (junction rule), not the second.

Option (3) Law of conservation of energy — Correct. The sum of potential changes round a loop being zero expresses conservation of energy.

Option (4) Law of conservation of momentum — Incorrect. Momentum is not involved in either of Kirchhoff's laws.

Note: A similar question was also asked in CUET (UG) 2026 on 18-05-2026 (Slot 1).

NCERT (2026-27):
Kirchhoff’s Rules – “… (b) Loop rule: The algebraic sum of changes in potential around any closed loop involving resistors and cells in the loop is zero (Fig. 3.15). This rule is also obvious, since electric potential is dependent on the location of the point. Thus starting with any point if we come back to the same point, the total change must be zero.”