According to Kirchhoff's Current Law, what must be true about currents at a node?

According to Kirchhoff's Current Law, what must be true about currents at a node?

• A. The currents entering a node must equal the currents leaving the node.
• B. The currents must sum to the battery voltage.
• C. The currents must be all positive numbers.
• D. The currents are independent of each other.

Answer: (A)

At a node, charge balance requires that currents flowing into the node equal currents flowing out. In a steady-state circuit, charge can’t pile up at a point, so the total current entering through some branches must be exactly carried away by the other branches. If you assign a direction to each branch, the algebraic sum of those currents at the node is zero, meaning the in-flows and out-flows balance. This is why the statement about currents entering equaling currents leaving is the right one. The idea that currents must sum to a battery voltage isn’t related to current balance at a node (that would be about Kirchhoff’s Voltage Law). Currents don’t have to be all positive—signs just reflect chosen directions, and a current can be negative relative to your reference. And the currents at a node aren’t independent; they’re constrained by the need to balance at that point.

At a node, charge balance requires that currents flowing into the node equal currents flowing out. In a steady-state circuit, charge can’t pile up at a point, so the total current entering through some branches must be exactly carried away by the other branches. If you assign a direction to each branch, the algebraic sum of those currents at the node is zero, meaning the in-flows and out-flows balance.

This is why the statement about currents entering equaling currents leaving is the right one. The idea that currents must sum to a battery voltage isn’t related to current balance at a node (that would be about Kirchhoff’s Voltage Law). Currents don’t have to be all positive—signs just reflect chosen directions, and a current can be negative relative to your reference. And the currents at a node aren’t independent; they’re constrained by the need to balance at that point.