Definition

Kirchhoff's Voltage Law

The algebraic sum of all voltages around a complete loop in a circuit is equal to zero.

It makes no difference where you begin nor the direction you go around the loop. In this example we begin at the bottom of the negative end of the 18V device, then proceed clockwise through the two remaining devices. The result is:

-18V + 12V + 6V = 0

Those values algebraically add to 0.

To show that the direction makes no difference, use the same starting point, but move in the counterclockwise direction. The result is:

-6 � 12 + 18 = 0