Kirchhoff's voltage law (KVL) states what about voltages in a closed loop?

• A. The sum of currents at a junction equals zero
• B. The sum of voltages around any closed loop equals zero
• C. Power equals current times resistance
• D. The voltage across a component equals current times resistance

Answer: (B)

Kirchhoff's voltage law says that the sum of all voltages around a closed loop equals zero. This reflects conservation of energy: as you traverse the loop, every voltage rise from sources must be exactly balanced by voltage drops across the other elements, so the total change in electric potential around the loop is zero. Using a consistent sign convention, you treat a rise as positive and a drop as negative, and the equation around any loop sums to zero.

This means that in any loop, the voltage supplied by sources equals the total voltage dropped across all elements like resistors. For example, a battery providing a certain voltage must be offset by the IR drops in the loop so that the net voltage is zero.

The other statements describe different ideas: one is Kirchhoff’s current law, which concerns how currents split and join at a junction; another is a general power relationship, and the last is Ohm’s law for a resistor. They’re related concepts, but they don’t express the rule about the sum of voltages around a loop.