In linear, direct current circuits, strength of the current is directly proportional to the voltage, and inversely proportional to the resistance: I = V/R.

Of all the theories concerning electricity, this law developed by Georg Simon Ohm remains the most practical to the electrical industry. IBEW apprentices throughout the United States and world continue to learn its applications.

The road to recognition for this law was long and hard for Ohm, born the son of a master locksmith on March 16, 1789, in Erlangen, Bavaria.

Ohm and his older brother Martin enrolled in the University of Erlangen, but a family disagreement over Ohm’s conduct put his education on hold for a time. As a result, he spent time supporting himself as a tutor, later returning to the university to earn a Doctor of Philosophy degree. Soon after, he secured a teaching post at a secondary school in Bamberg, but the school soon closed in the aftermath of the Napoleonic Wars.

Ohm secured another post at the Jesuit Gymnasium of Cologne, which provided well-equipped laboratories and access to the published works of mathematicians and scientists of the time, including Oersted, whose discoveries concerned electromagnetism. The academic environment stimulated Ohm to begin experimenting with electricity, magnetism and galvanic circuits.

Though Ohm was heavily burdened by teaching responsibilities, he still managed to explore such questions as: what were the conducting powers of wires and other conductors? What was the effect of different metals, various lengths and dimensions on electric flow? How did this affect the output of a battery in terms of current running through a circuit?

Using a Coulomb torsion balance galvanometer, Ohm conducted experiments to calculate the resistance of a circuit using an equation involving the ratio of voltage to current and considering length and dimension or wire. He published his findings in two papers in February and April of 1826.

The second paper offered an iteration of what came to be known as Ohm’s Law. His theory of how electrical current might utilize the volume, structure and conductivity of various metal wires was based on concepts of heat conductivity as well as an understanding of electricity as fluid in nature.

Ohm also built upon the scientific contributions of Alessandro Volta and Andre Marie Ampere.

Volta had developed the electric pile or battery, which provided a sustained supply of electricity, and his name is synonymous with the volt—the unit of electromotive force that drives current. Ampere identified the tension between the terminals of a battery as “electric potential.”

Ohm’s book, “Die galvanische Kette, mathematisch bearbeitet” or “The Galvanic Circuit Mathematically Investigated,” published in 1827, garnered a hostile reception from Berlin’s academic establishment. One critic branded it “a web of naked fancies.” Another said it was “the result of an incurable delusion, whose sole effort is to detract from nature.”

Younger scientists in America, Russia and England, however, confirmed the validity of Ohm’s work. In 1841, he was awarded the Copley Medal from the Royal Society of London.

Ohm never married. He died in 1854 at age 65, but in 1862 the British Association Committee on Standards of Electrical Resistance adopted the “Ohmad” as a standard of electrical resistance. The unit of electrical resistance in the International System of Units later came to be known more simply as the ohm, symbolized by the uppercase Greek letter omega, Ω.

With mass implementation of alternating current, Ohm’s Law assumed a new form: I=V/Z, with Z being the apparent resistance that is no longer constant.