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Kirchhoff
(ˈkɪətʃɒf, ‖ ˈkɪrxhɔf)
Also (erron.) Kirchoff.
The name of Gustav Robert Kirchhoff (1824–87), Ger. physicist, used in Kirchhoff's law: a. Electr. Either of two laws concerning electric networks in which steady currents are flowing: (a) (the first law) the algebraic sum of the currents in all the conductors that meet in a point is zero; (b) (the second law) the algebraic sum of the products of current and resistance in each part of any closed path in a network is equal to the algebraic sum of the e.m.f.s in the path.
1869R. Main Rudimentary Astron. (new ed.) 164 (heading) Kirchhoff's law. Ibid. p. xx (heading) Application of Kirchhoff's law. 1876H. R. Kempe Handbk. Electr. Testing v. 45 Kirchoff's laws.., though exceedingly simple.., are not so well known as they ought to be. 1905W. C. D. Whetham Theory Exper. Electr. v. 117 The principles of continuous current-flow which we have now established may conveniently be applied to complex circuits and networks of conductors in the form of two statements known as Kirchhoff's laws. 1970M. Nelkon Electr. v. 130 Kirchhoff's first law is a mathematical statement of the fact that the charges do not accumulate at any junction of an electrical circuit. Ibid. 132 We need to apply Kirchhoff's second law to two complete circuits as there are two unknowns.
b. Physics. The law that the absorptivity of a body for radiant energy of any particular wavelength is equal to its emissivity at the same temperature for the same wavelength.
1901G. K. Burgess tr. Le Chatelier & Boudouard's High-Temperature Measurements viii. 140 (heading) Kirchoff's law. 1945F. A. Berry et al. Handbk. Meteorol. iv. 288 It is an immediate consequence of Kirchhoff's law that the intensity emitted by a body can never exceed the black-body intensity and can equal it only in the spectral regions where the body is opaque. 1967R. W. Fairbridge Encycl. Atmospheric Sci. 793/1 We assume black-body radiation which is that of a body that is characterized by maximum possible absorption at all incident wavelengths, insuring maximum emissivity according to Kirchoff's Law. |