Kirchhoff's current law (KCL) states what about currents at a junction?

• A. The sum of voltages around a loop equals zero
• B. The sum of currents entering a junction equals the sum leaving
• C. Power equals voltage times current
• D. Resistance equals voltage divided by current

Answer: (B)

At a junction, currents must balance because electric charge is conserved and a node can’t store charge in steady state. This means the total current flowing into the junction equals the total current flowing out. When you analyze circuits, you assign a direction to each current and the algebraic sum of all currents at the node is zero. For example, if currents come in from some branches and split to others, the sum entering equals the sum leaving.

This is Kirchhoff’s current law. The other statements describe different ideas: the sum of voltages around a loop equals zero is Kirchhoff’s voltage law; power equals voltage times current is a basic power relation; resistance equals voltage divided by current is Ohm’s law for a resistor.