Which statement expresses Kirchhoff's current law (KCL)?

Which statement expresses Kirchhoff's current law (KCL)?

• A. Sum of voltages around a closed loop equals zero.
• B. Sum of currents into a node equals the sum leaving (net zero).
• C. Ohm's law relates voltage to current and resistance.
• D. The magnetic flux through a loop is constant.

Answer: (B)

Kirchhoff's current law focuses on charge conservation at a junction. At any node where wires meet, the total current flowing into the node must equal the total current flowing out. When you account for direction, the net current at that node is zero, so the algebraic sum of currents is zero. This is exactly what the statement “the sum of currents into a node equals the sum leaving (net zero)” expresses, and it underpins how currents combine and split in circuits. In steady circuits, charge doesn’t pile up at a point, so incoming current must be matched by outgoing current. That’s why this description is the appropriate one for KCL. The other ideas aren’t about current balance at a node: summing voltages around a closed loop is Kirchhoff’s voltage law, which deals with voltages in loops; Ohm’s law relates voltage, current, and resistance for a single element rather than at a node; and magnetic flux through a loop relates to magnetic effects, not the current balance at a junction.

Kirchhoff's current law focuses on charge conservation at a junction. At any node where wires meet, the total current flowing into the node must equal the total current flowing out. When you account for direction, the net current at that node is zero, so the algebraic sum of currents is zero. This is exactly what the statement “the sum of currents into a node equals the sum leaving (net zero)” expresses, and it underpins how currents combine and split in circuits.

In steady circuits, charge doesn’t pile up at a point, so incoming current must be matched by outgoing current. That’s why this description is the appropriate one for KCL.

The other ideas aren’t about current balance at a node: summing voltages around a closed loop is Kirchhoff’s voltage law, which deals with voltages in loops; Ohm’s law relates voltage, current, and resistance for a single element rather than at a node; and magnetic flux through a loop relates to magnetic effects, not the current balance at a junction.