A node in a circuit has currents I1 = 2 A and I2 = 3 A entering, and I3 leaving. What is I3 by Kirchhoff's current law?

A node in a circuit has currents I1 = 2 A and I2 = 3 A entering, and I3 leaving. What is I3 by Kirchhoff's current law?

• A. 5 A
• B. 1 A
• C. 8 A
• D. -5 A

Answer: (A)

At a node, currents entering must equal currents leaving. Here, I1 and I2 are entering, while I3 is leaving. The leaving current must balance the two entering currents, so I3 equals I1 plus I2: 2 A + 3 A = 5 A. Since I3 is specified to be leaving, the magnitude 5 A in that outward direction satisfies the balance. If you try other values, they won’t satisfy the condition that the total entering equals the total leaving with the given directions.

At a node, currents entering must equal currents leaving. Here, I1 and I2 are entering, while I3 is leaving. The leaving current must balance the two entering currents, so I3 equals I1 plus I2: 2 A + 3 A = 5 A. Since I3 is specified to be leaving, the magnitude 5 A in that outward direction satisfies the balance. If you try other values, they won’t satisfy the condition that the total entering equals the total leaving with the given directions.