Georg Simon Ohm and the basis for circuit theory

Georg Simon Ohm (1789-1854) was an educator, mathematician and theoretician, but above all he was an experimenter. Ohm’s law, relating electrical force, current and resistance in a circuit, was based on empirical data – careful experiments, measurements and records that he kept. Ohm’s thoroughness was consistent with that of his colleagues and the time in which they lived. It may be seen as the result of French influence where observed empirical data trumped appeal to past authority. The period was marked by a continuous migration away from animistic explanations that relied on unquestioned a priori concepts.

Ohm’s first important paper published in 1825. In it he quantified the amount of electromagnetic force measurable at the end of wires of varying lengths. The amounts were based on observation rather than theory.

In 1826, Ohm described electrical conduction, inspired by Charles Fourier’s earlier studies in heat conduction.

The major breakthrough of Ohm’s Law appeared in 1827. In The Galvanic Circuit Investigated Mathematically, Ohm laid out his entire theory of electricity. What must be understood is that previously research results pertaining to electrical phenomena had been presented mostly in a non-mathematical format. Of necessity, then, the first part of the book explicates the mathematical tools necessary so  that mid-nineteenth century readers could comprehend the relationships that Ohm went on to expound.

Ohm’s law states:
E = I × R
Where E = electrical force, V; I = in the language of the time, intensity, A; R = resistance, Ω. Using elementary algebraic techniques, the equation can be arranged so any of the three terms can stand alone on the left side, as an unknown.

The Ohm’s law wheel is a convenient circular tabulation that lets someone visualize all the derived equations along with the power equation, where power in watts is the product of current and voltage.

Less than 20 years after Ohm defined his law, Gustav Robert Kirchhoff formulated a series of laws that simplify complex circuits such as those with more than one power source. These circuits conform to Ohm’s law but, without Kirchhoff’s simplifications, the mathematics can become overwhelming.

Today  the unit of resistance, ohm, in the SI system is named after Georg Simon Ohm. One volt will cause one amp of current to flow through a load whose resistance is one ohm. The relationship sounds simple today, but the insight was the culmination of research spanning many centuries.