Which statement correctly defines Kirchhoff's voltage law?

• A. KVL states the sum of voltages around a closed loop equals zero.
• B. KVL states the sum of currents around a closed loop equals zero.
• C. KVL relates power to current.
• D. KVL states the voltage across all elements in a loop equals the supply voltage.

Answer: (A)

Kirchhoff's voltage law states that the algebraic sum of all voltages around any closed loop is zero. As you move around a loop, every voltage rise and every voltage drop must balance out so you return to the same potential you started with. The sign you assign for each element depends on your traversal direction, but the total—including sources and drops across resistors or other components—adds up to zero. This reflects energy conservation: the energy supplied by sources in the loop is exactly consumed by the elements in the loop.

For example, a loop with a 10-volt source and two resistors that drop 4 V and 6 V satisfies KVL because the rises and drops add up as +10 V minus 4 V minus 6 V equals zero.

Other statements aren’t KVL: currents around a loop aren’t what KVL describes (that’s Kirchhoff’s current law at nodes), and the relation P = VI connects power to voltage and current but isn’t about the loop voltage balance. A claim that the voltage across all elements in a loop equals the supply voltage misstates the law; the correct idea is that the sum of all voltages around the loop is zero, which effectively means the total drops balance the sources when signed consistently.