Kirchhoff's second law states that the sum of all voltages around any closed loop in a circuit must equal what?

Kirchhoff's second law, also known as the loop rule, states that the sum of all voltages around any closed loop in a circuit must equal zero. This principle arises from the law of conservation of energy, which asserts that energy supplied in a closed loop must equal energy consumed. In a circuit, as you traverse a loop, any voltage gains from sources (like batteries) must be offset by voltage drops across circuit elements (such as resistors and other components). Therefore, when you sum all the voltage contributions within that loop, the total must equal zero, reflecting the balance of energy within that closed system. This understanding is crucial for analyzing complex electrical circuits and ensuring that they function correctly according to fundamental electrical principles.