Georg Simon Ohm

German physicist

• Born: March 16, 1789; Erlangen, Holy Roman Empire
• Died: July 6, 1854; Munich, Germany

Nineteenth-century German mathematician and physicist Georg Simon Ohm was responsible for the discovery of Ohm’s law, which describes the exact relationship of potential, or voltage, and current in electric conduction. The international unit of resistance, the ohm, is named after him.

Primary fields: Mathematics; physics

Specialties: Electromagnetism; acoustics

Early Life

Georg Simon Ohm was born into a working-class family living in Erlangen, Bavaria, in what is now Germany, on March 16, 1789. His father, Johann Wolfgang Ohm, was a locksmith and master mechanic; his mother, Maria Elizabeth Beck, was a tailor’s daughter. The Ohms had seven children, but only two besides Georg survived into adulthood. Martin, Ohm’s younger brother, would become a noted mathematician.

Though he was not formally educated, Ohm’s father learned all he could about mathematics, physics, and philosophy, among other subjects, and sought to instill this same love of learning in his children. In fact, Ohm likely gained more insight into scientific matters from his father than he did at the Erlangen gymnasium, the local school he attended.

In 1805, Ohm entered the University of Erlangen. Mathematics professor Karl Christian von Langsdorf, a respected German mathematician, geologist, natural scientist, and engineer, was so impressed with both Ohm and his brother that he compared them favorably to the Bernoullis, a family of scholars from Basel, Switzerland. At the university, however, Ohm showed more promise than achievement, preferring pastimes like billiards, ice-skating, and dancing to his studies. After three semesters, angered by his son’s behavior, Ohm’s father demanded that he leave the university and get a job.

Ohm found work as a mathematics teacher at a school in Gottstadt bei Nydau, Switzerland, in 1806. In his free time, he began to study the works of great mathematicians. His passion for learning reinvigorated, he decided to leave his teaching position in 1809 to become a private tutor in Neuchâtel, Switzerland, so he could more fully commit himself to his studies. Ohm eventually returned to the University of Erlangen, where he earned his doctorate in 1811. He then worked as an unpaid lecturer at the university for three semesters. In 1813, he landed a job teaching physics and mathematics at a school in Bamberg run by the Bavarian government. The position did not make Ohm happy, as he believed he could do far better for himself. To improve his prospects, he wrote a geometry textbook, but he continued to work at the school until it closed in 1816.

Life’s Work

After the Bamberg school closed, Ohm took a position teaching physics and mathematics at the Jesuit gymnasium in Cologne, Germany, in 1817. Surrounded by excellent equipment, he began to conduct experiments related to electricity and magnetism, which led him to start exploring electric circuits.

In his free time, Ohm read the work of such noted French mathematicians as Joseph-Louis Lagrange, Jean-Baptiste Biot, and Joseph Fourier, among others. In 1820, Danish chemist and physicist Hans Christian Ørsted discovered that electricity and magnetism are related because electric currents create magnetic fields; this discovery likely inspired Ohm in his own work.

By 1825, the standards at the gymnasium where Ohm taught were faltering, and Ohm changed his approach to experimentation as he continued to work toward his dream of a professorship at an esteemed university. Rather than continuing to experiment for his own pleasure and knowledge, he began conducting experiments with an eye toward publication, which he believed would help him earn a better teaching position. His first scientific paper, published in 1825, describes how the electromagnetic force produced by a wire decreases as the wire’s length increases. Unfortunately, this paper presents an incorrect mathematical formula for this conclusion. A year later, Ohm fixed his mistake and produced a new paper in which his revised formula not only is backed up by experimental evidence but also applies to numerous phenomena connected to electromagnetism.

What came to be known as Ohm’s law is a mathematical equation describing the relationship of electrical current, resistance, and voltage. It helped to explain not only Ohm’s work but also the work of a number of other scientists who were then working on galvanic, or direct-current, electricity. In 1827, Ohm published Die galvanische Kette, mathematisch bearbeitet (The Galvanic Circuit Investigated Mathematically, 1841), in which he presented the now-famous mathematical formula I = V / R. Put simply, this formula states that an electrical current (I) going through a conductor is directly proportional to the voltage (V) and inversely proportional to the resistance (R).

The first section of Ohm’s books explains the mathematics behind his experiments, which used various lengths of wire to prove his formula. Though his work was accurate, Ohm’s book was met with indifference, if not outright hostility, because most German physicists at the time knew little of mathematics and did not believe math applied to their discipline. When his employers reacted unenthusiastically to his work, Ohm resigned his teaching position in March 1828. His work would only belatedly be recognized.

In 1833, Ohm became a professor at the polytechnic school in Nuremberg. Two years later, he began serving as chairman of mathematics at the University of Erlangen and became inspector of scientific education for Bavaria. In 1841, the Royal Society of London presented Ohm with the Copley Medal and granted him membership. He received memberships from a number of other scientific associations in the following years. In 1849, he became a professor at the University of Munich in Germany; he would later become physics chair. For Ohm, his appointment in Munich was the achievement of a lifelong dream.

In his final years, Ohm was interested in acoustics and optics. His acoustical work was eventually discredited by August Seebeck, a well-known physicist. Ohm was working on a textbook on optics when he died in Munich on July 6, 1854. After his death, the international unit of electrical resistance, the ohm, was named after him.

Impact

Ohm’s use of mathematics to prove his theory pertaining to electrical resistance redefined the way scientists of his era, and German physicists in particular, approached physics. Prior to Ohm, physics was studied in a nonmathematical way. Ohm’s work was initially dismissed by many physicists, but within a generation or so, the mathematics behind Ohm’s law helped to support the idea that mathematics and physics were complimentary disciplines.

While many people may know that Ohm’s law is important in the field of electrical circuits, allowing, for example, engineers to understand how voltage, current, and resistance work on a large scale, the law also functions on the atomic level, where it is used by physicists looking at the electrical properties of microscopic particles. Researchers have detected Ohm’s law at work in silicon wires that are no more than an atom high and four atoms wide.

Bibliography

Mann, Friedrich. George Simon Ohm. Trans. Irmeli Kuehnel. Seattle: Pentode, 2007. Print. Provides a detailed account of Ohm’s life and work, with a translation that demonstrates how Ohm’s law is essential to a modern understanding of electronic circuits.

Paynter, Robert T., and B. J. Toby Boydell. Introduction to Electricity. Upper Saddle River: Pearson, 2011. Print. Presents an overview of all basic scientific principles pertaining to electricity, including the importance of Ohm’s law. Contains illustrations, step-by-step examples, and illustrated examples of applications.