198th birthday of Gustav Kirchhoff


Today we celebrate the 198th anniversary of the German physicist Gustav Kirchhoff who was born on March 12, 1824.

We highlight his contribution to the theory of electrical circuits, through the postulation of Kirchhoff’s Laws, valid in the time and frequency domains, and the basis for network analysis:

Kirchhoff’s current law: The algebraic sum of all the currents in an electrical node is equal to zero.

Kirchhoff’s voltage law: The algebraic sum of the potential differences (voltages) in a closed loop is equal to zero.

Both Kirchhoff’s Laws can be interpreted as corollaries of Maxwell’s Equations applicable for low frequencies: direct current DC or alternating current AC for frequencies where the wavelength of the electromagnetic radiation is much greater than the physical lengths of the circuits.

For example, for a network frequency of 50 Hz, Kirchhoff’s Laws will be valid for distances L << λ = c / f = 300,000 Km/s / 50Hz = 6,000 Km.

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