Kirchoffs Law

Kirchoff's Law

Gustav Kirchoff in 1845 developed a set of laws popularly known as Kirchoff's Law. Kirchoff's Voltage Law (KVL) and Kirchoff's Current Law (KCL) generally deal with the conservation of energy and current within the Electrical Circuits. Before going to the laws, let’s understand some of the terms associated with a DC circuit.

• Electrical Circuit: is composed of components through which electric current can flow.
• Path: A path can be defined as a single line of connecting voltage or current sources and components.
• Node:  Can be defined as any points on the circuit were two or more circuit components meet.
• Branch: A branch represents a single component of the circuit.
• Loop: is defined as the closed path inside a circuit.
• Mesh: is a loop inside the circuit that does not contain any other loop.

Kirchoff's Current Law

This law is also known as Kirchoff's Junction Rule, Kirchoff's Point Rule or Kirchoff's First Law.

The law states that:

“For any node in an electrical circuit, the sum of currents flowing out of that node is equal to the sum of currents flowing into that node” or it can be stated as “The algebraic sum of currents in a network meeting at a point is zero”.

Kirchoff's Voltage Law

This law is popularly known by the names Kirchoff's second law, Kirchoff's Mesh Rule and Kirchoff's Loop Rule.

The law states that:

“Algebraic sum of the products of the resistances and currents in a closed loop is equal to the total emf available in that loop” or “The directed sum of potential differences around any closed circuit is zero” or “In simple words, the sum of emf in any closed loop is equal to the sum of the potential drops in that loop”.

Disadvantages of Kirchoff's Law

• KCL and KVL are not good for high frequency AC circuits.
• KCL is valid only if the total electric charge is constant in the circuit.
• KVL is based on the assumption that there is no changing magnetic field within the closed circuit.

Applications of Kirchoff's Law

Kirchoff's Laws are used to find the currents and voltages associated within a DC circuit. Its simplicity and ease of calculation helps to find the results.