Researched and written by: Aleksey Moshkov, Lead Engineer for EnvisionSTEM
Kirchhoff's laws are two common principles in electrical engineering, which describe the behavior of current and voltage in a circuit. These laws were first introduced by Gustav Kirchhoff in 1845 and are widely used in electrical engineering to analyze and design circuits. Kirchhoff's laws can be applied to any electrical circuit, whether it is a simple circuit with just a few components or a complex circuit with many components and branches.
Kirchhoff's Current Law:
Kirchhoff's first law is his current law (Kirchhoff's Current Law), which states that the sum of currents entering any node or junction in a circuit must equal the sum of currents leaving that node. In other words, the total current flowing into a node must be equal to the total current flowing out of the node. Kirchhoff's Current Law is based on the fundamental concept in physics that charge will always be conserved. This law is essential for determining the current through each component in a circuit.
Image credits: Nicole Foto
As seen in the junction above, the two resulting currents (3 Amperes and 2 Amperes) must add up to the input current (5 Amperes).
Kirchhoff's Voltage Law:
According to Kirchhoff's second law, Kirchhoff's Voltage Law, the sum of voltages around any closed loop in a circuit must equal zero. In other words, the total voltage drops across all the components in a closed loop must add up to the total voltage supplied to the loop. Kirchhoff's Voltage Law is based on the principle of conservation of energy. It states that the total voltage around any closed loop in a circuit must be zero. This law is essential for determining the voltage drop across each component in a circuit.
Image credits: Nicole Foto
As seen in the circuit above, the sum of all the voltage drops on the loads (resistors in this case) in the first and second loop must be equal to zero. In the first loop, there is a voltage gain in the battery, then voltage drops in resistors R1, R4, and R6. In the first loop, there is a voltage gain in resistor R4, then voltage drops in resistors R2, R3, and R5.
In the first loop, R1 + R4 + R6 - 6V = 0V
In the second loop, R2 + R3 + R5 - R4 = 0V
In conclusion, Kirchhoff's laws have been widely used in electrical engineering for over a century to analyze and design circuits. Kirchhoff's Current Law states that the sum of currents entering any node in a circuit must equal the sum of currents leaving that node, while Kirchhoff's Voltage Law states that the sum of voltages around any closed loop in a circuit must equal zero. Kirchhoff's laws continue to be a fundamental tool for engineers and scientists across various fields and will likely remain so for many years to come.
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