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In the loop diagram, starting from the source and moving once around the circuit, why must the net potential change return to zero? 
ABecause current is the same everywhere in the circuit
BBecause resistance cancels automatically in every loop
CBecause electric potential is a state quantity, so returning to the starting point gives no net change
DBecause each resistor has equal voltage across it
Answer & Solution
Correct answer: C. Because electric potential is a state quantity, so returning to the starting point gives no net change
Potential difference depends on initial and final points. In a closed loop, you return to the same point, so the net change in potential must be zero. This is the conceptual basis of KVL and is tied to conservation of energy, not equal currents or equal resistor voltages.