Kirchhoff's Voltage Law

Kirchhoff's voltage law, or KVL, is based on the principle of energy conservation.

It states that the algebraic sum of all voltages around a closed path or loop within a circuit is zero.

The direction of the loop around the circuit could be clockwise or counterclockwise and can start from anywhere.

Once the loop direction is chosen, positive voltages have their negative terminal encountered first, and negative voltages have their positive terminal encountered first.

Applying KVL to each loop and rearranging the terms gives its alternative form, which states that the sum of voltage drop equals the sum of supplied voltages.

For example, consider christmas tree lights where three LED lights connected in series are strung together.

If each light requires three volts to turn on, the voltage needed for the battery to power these lights is determined by applying KVL.

The battery voltage equals the sum of the voltage drop across the three lights.