What does Kirchhoff's voltage law state about voltages in a closed loop?

Kirchhoff's voltage law states that in any closed loop or mesh in an electrical circuit, the sum of the electrical potential differences (voltages) around that loop must equal zero. This principle is based on the conservation of energy, which implies that the energy supplied by sources (like batteries) is fully accounted for by the energy used in the circuit elements (like resistors, capacitors, etc.) over one complete loop.

In practical terms, as you traverse a closed loop, the voltage increases when moving through battery sources and decreases when passing through components that consume voltage—this creates a balance that results in the total sum being zero. Therefore, any increase in voltage due to sources must be offset by the decreases due to other components, aligning with the law's core assertion.