# Bestimmung des Gesetzes.

**Publisher Information: **Halle: Expedition des Vereins, 1826.

Announcing a Comprehensive Law for Electric Current

Ohm, Georg Simon (1789-1854). Bestimmung des Gesetzes, nach welchem Metalle die Contaktelectricitat leiten, nebst einem Entwurf zu einer Theorie des Voltaischen Apparates und des Schweiggerschen Multiplicators. In Jahrb. d. Chemie u. Physik 16 (1826): 137-66, plus plate figures 1-2 on plate III. Whole volume, 8vo. xvi, 496pp.2 folding printed charts, 3 folding engraved plates. Halle: In der Expedition des Vereins zur Verbreitung von Naturkenntniss, 1826. 201 x 122 mm. Half sheep c. 1826, a bit rubbed, light wear to corners & edges. Minor foxing, otherwise very good.

First Edition. Ohm began publishing his electricity researches in 1825 with his "Vorlaufige Anzeige des Gesetzes, nach welchem Metalle die Contaktelektricitat leiten," a paper in which he sought to find a functional relationship between the decrease in the electromagnetic force exerted by a current-carrying wire and the length of the wire. Although this paper contained some fundamental errors, it was remarkable for its direct foundation on experiment, a characteristic of all Ohm's early papers. In February and April of the following year Ohm published two important papers dealing separately with the two major aspects of his theory of galvanic electricity, which he would later unify in his landmark Die galvanische Kette (1827).

The first paper, which we are offering here, "announced a comprehensive law for electric current that brought order into the hitherto confused collection of phenomena pertaining to the closed circuit, including the solution to the problem of conductibility as he and others had conceived of it" (DSB).

Ohm's second paper, "Versuch einer Theorie der durch galvanische Krafte hervorgebrachten elektroskopischen Erscheinungen" (Ann. Phys. 6 [1826]: 459-69; 7, 45-54, 117-18), "broke new ground in associating an electric tension with both open and closed galvanic circuits" (DSB), and contained the first statement of Ohm's Law.

"Ohm's experimental procedure in ["Bestimmung des Gesetzes"] was analogous to that which he had used earlier but was modified in several significant ways. First, at Poggendorff's suggestion, he now used a thermoelectric pile in order to eliminate the fluctuations in current strength accompanying the voltaic pile, fluctuations that Ohm attributed to changes produced by the current in the distribution (Vertheilung) of the components in the liquid conductor. Second, he sought a direct relationship between the electromagnetic force of the current and the entire length of the connecting wire. . . . "[I]n the paper in question Ohm simply observed that the data from each of his several sets of experiments were very closely represented by the formula X = a/(b + x), where X is the strength of the electromagnetic effect-which he took as a measure of the electric current-of a conductor of length x on the magnetic needle of a Coulomb torsion balance, and where a and b are constants the exact nature of which he proposed to determine from additional series of carefully controlled experiments. The observation that b remained constant for all series of experiments, whereas a varied with temperature, led Ohm to conclude that a depended solely on the electromotive force (erregende Kraft) of the pile and b solely on the resistance (Leitungswiderstand or, more commonly, Widerstandslange) of the remaining portion of the circuit, in particular that of the pile itself. He also observed that the electromotive force of the thermoelectric pile appeared to be exactly proportional to the temperature difference at its end points. . . . "

"After reconfirming the validity of his law by further series of experiments, Ohm exhibited its explanatory powers on some of the chief unsolved problems which had occupied scientists working on the pile; and he showed how it also cast light on a number of other previously reported but poorly understood experimental findings. . . . The fruitful application of Ohm's simple law to existing problems was an explanatory tour de force" (DSB).

**Book Id:**38339

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