Which statement correctly defines Kirchhoff's Current Law (KCL)?

• A. The sum of currents entering a node equals the sum leaving.
• B. The sum of voltages around a closed loop equals the supply voltage.
• C. The voltage across a resistor equals the current through it times the resistance.
• D. The power in a circuit equals voltage times current.

Answer: (A)

At a junction where several wires meet, currents must balance because charge cannot build up at a point in steady state. This is Kirchhoff's Current Law: the total current flowing into the junction equals the total current flowing out. In practice, you can think of currents as having a chosen sign convention; if two currents enter the node and one leaves, the entering currents must sum to the leaving current (for example, i1 + i2 = i3).

This rule is a direct consequence of conservation of charge and is fundamental for solving circuits using node-voltage analysis, where you write an equation at each node to reflect that net current is zero.

The other statements describe different electrical relationships. One refers to the sum of voltages around a closed loop (Kirchhoff's Voltage Law), which governs loops of voltage rather than currents at a node. Another states Ohm's law for a resistor (voltage equals current times resistance), which relates V, I, and R for a component, not the balance of currents at a junction. The last one expresses electrical power as voltage times current, which is a power relation, not a current-balance law.