DC Network Theorems Unit 3 – Kirchhoff's Voltage Law
Kirchhoff's voltage law may be stated in two ways.
- The sum of all the voltage drops in a series circuit equals the circuit applied (source) voltage.
For example, in this circuit, the sum of all voltage drops is 20V (10 + 7 + 3). The source voltage
is also 20V. Because the sum of the voltage drops equals the source voltage, the first requirement
of Kirchhoff's law is met.
Kirchhoff's voltage law may be stated a second way.
- The algebraic sum of the voltage source(s) and voltage drops in a series circuit equals zero.
For example, in this circuit, voltage drops are assigned a negative (-) polarity, and the voltage
source is assigned a positive (+) polarity. Combining all voltages algebraically results in 0
(+20 - 10 - 7 - 3 = 0). Because the algebraic sum of all voltages in the loop is zero, the second
requirement of Kirchhoff's law is met.