Kirchhoff's Law

Kirchhoff's Law: Electric circuits generally consist of a large number of resistors and cells interconnected sometimes in a very complicated manner. There are many formulae related to series and parallel combinations of resistors but those are not always sufficient to determine all the currents and potential differences in the circuit. The law called Kirchhoff’s law is very useful for the analysis of electric circuits. The concept of Kirchhoff's law was given by German physicist Gustav Kirchhoff in the year 1845. Kirchhoff's law is related to how the current flows through the circuit and how the voltage varies through the loop. So Gustave Kirchhoff gave two laws, that is,-

1. Kirchhoff's current Law- Also called Kirchhoff's first law or Kirchhoff's junction rule. It states that “In a circuit, the sum of current flowing into the node(junction) is equal to the sum of currents flowing out of that node”.
2. Kirchhoff's Voltage Law- Also referred to as Kirchhoff's second law or Kirchhoff's Loop rule. It says that “The sum of voltage around any closed loop is zero”.

Kirchhoff's Current Law

According to Kirchhoff’s Current Law,

“The sum of current entering a junction or a node is equal to the sum of current leaving the node as no charge is lost.”

Suppose I1, and I2 are current that flows into the node of the electrical circuit and I3 and I4 are current that flows out of the circuit. Then according to Kirchoff's current law:

I1 + I2 = I3 + I4

Kirchhoff's Voltage Law

According to Kirchhoff's Voltage Law,

“The sum of voltage around any closed loop is zero”.

When you start at any point of the loop and further continue in the same direction, the voltage drops in all the negative or positive directions and finally returns to the same point. It is necessary to maintain the direction either counterclockwise or clockwise. If such a condition of direction is not maintained then the net value of voltage will not become zero. Such voltage law can also be applied in the analysis of circuits in series.

Limitation of Kirchhoff's Law

The limitation related to Kirchhoff's law is that it is only applicable when there is the absence of fluctuating magnetic field. this means that in the presence of fluctuating magnetic field this law does not apply.

Applications of Kirchhoff's Law

Some of the application of Kirchhoff's law is-

• Wheatstone bridge is the foremost application of Kirchhoff's Law.
• This law is capable of calculating the unknown values f current and voltage in the circuit.
• With the help of Kirchhoff's law calculation of complicated circuits is possible.
Kirchhoff's Law- FAQs

Ans. The concept of Kirchhoff's law was given by German physicist Gustav Kirchhoff in the year 1845.

Ans. Also called Kirchhoff's first law or Kirchhoff's junction rule. It states that “In an electrical circuit any current flowing into the node(junction) is equal to the sum of currents flowing out of that node”.

Ans. Also called Kirchhoff's second law or Kirchhoff's Loop rule. It states that “The sum of voltage around any closed loop is zero”.

Ans. The limitation related to Kirchoff's law is that it is only applicable when there is the absence of fluctuating magnetic field. this means that in the presence of fluctuating magnetic field this law does not apply.

Ans. Some of the application of Kirchhoff's law is- Wheatstone bridge is the foremost application of Kirchhoff's Law, This law is capable of calculating the unknown values f current and voltage in the circuit, With the help of Kirchhoff's law calculation of complicated circuits is possible.