Gustav Robert Kirchhoff (March 12, 1824 – October 17, 1887) was a German physicist
who contributed to the fundamental understanding of electrical circuits, spectroscopy,
and the emission of blackbody radiation by heated objects. He coined the term "black
body" radiation in 1862, and two sets of independent concepts in both circuit theory
and thermal emission are named "Kirchhoff's laws" after him.  Wikipedia
The concepts of Kirchhoff's Current Law and Kirchhoff's Voltage Law follow. Both
assume a totally contained system where energy is conserved.
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Kirchhoff's Current Law
Kirchhoff's Current Law (aka
Kirchhoff's 1st Law) is one of the fundamental principles in electrical
circuit theory. It's named after Gustav Kirchhoff, a German physicist who
formulated this law in the mid19th century. KCL is used to analyze and describe
the behavior of electric currents at junction points within electrical circuits.
The statement of Kirchhoff's Current Law is as follows:
"At any junction (or node) in an electrical circuit, the sum of the currents
entering the junction is equal to the sum of the currents leaving the junction."
In other words, when you consider a point in a circuit where multiple
conductors or wires meet (a node), the algebraic sum of the currents flowing
into that node is always equal to the algebraic sum of the currents flowing out
of that node. This law is based on the principle of conservation of electric
charge, which means that no electric charge is lost or created at a junction; it
simply flows in and out.
Mathematically, Kirchhoff's Current Law can be expressed as:
Σ (incoming currents) = Σ (outgoing currents)
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Kirchhoff's Voltage Law
Kirchhoff's Voltage Law (aka
Kirchhoff's 2nd Law) is one of the fundamental principles in electrical
circuit theory. It's named after Gustav Kirchhoff, a German physicist who formulated
this law in the mid19th century. KVL is used to analyze and describe the behavior
of voltage in closed electrical circuits.
The statement of Kirchhoff's Voltage Law is as follows:
"In any closed loop or mesh within an electrical circuit, the sum of the voltage
rises is equal to the sum of the voltage drops."
In other words, when you traverse a closed loop in a circuit and take into account
all the voltage sources (voltage rises) and voltageconsuming elements (voltage
drops) encountered along the way, the algebraic sum of these voltage changes is
always zero. This is based on the conservation of energy, which states that energy
cannot be created or destroyed but only transferred or transformed. In an electrical
circuit, the voltage changes account for the energy transfer, and KVL ensures that
no energy is lost or gained within a closed loop.
Mathematically, Kirchhoff's Voltage Law can be expressed as:
Σ (voltage rises) = Σ (voltage drops)
Posted September 8, 2023 (updated from original
post on
4/26/2001)
