Kirchhoff's Laws

Kirchhoff's laws deal with the conservation of energy and conservation of charge when applied to electrical circuits. Although named after Gustav Robert Kirchhoff, they are often also wrongly called Kirchoff's laws. Kirchhoff stated another set of laws, also known as Kirchhoff's laws, relating to radiation from incandescent objects, so to avoid ambiguity the electrical laws described in this article are sometimes known as Kirchhoff's rules. The two rules were first described in 1845. Both rules can be directly derivated from the Maxwell's equations.

Table of contents

1 Kirchhoff's first law
2 Kirchhoff's second law
3 Read further

Kirchhoff's first law

This law is also called Kirchhoff's current law, Kirchhoff's point rule and Kirchhoff's first rule.

The principle of conservation of electric charge implies that:

At any point in an electrical circuit, the sum of currentss flowing towards that point is equal to the sum of currents flowing away from that point.

Kirchhoff's second law

This law is also called Kirchhoff's voltage law, Kirchhoff's loop rule and Kirchhoff's second rule.

The principle of conservation of energy implies that:

The directed sum of the electrical potential differences around a circuit must sum to zero. Otherwise, it would be possible to build a perpetual motion machine that passed a current in a circle around the circuit.