Kirchhoff’s Current and Voltage Laws

KCL (Kirchhoff’s Current Law) The sum of the currents entering a node equals the sum of the currents exiting a node.

Node

Application of KCL I 1 = 2A I 2 = 3A I 3 = 5A

I 1 = ? I 2 = 150 mA I 3 = 250 mA Problem w/KCL

KVL (Kirchhoff’s Voltage Law) The sum of the potential differences around a closed loop equals zero.

Closed Loop #1

Closed Loop #2

Closed Loop #3

Closed Loop #4

Not Closed #1

Not Closed #2

What KVL Really Means Sum of the Voltage drops across resistors equals the Supply Voltage in a Loop.

KVL #1

KVL #2