Georg Simon Ohm Biography

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World of Physics on Georg Simon Ohm

A single discovery established Georg Ohm's claim to fame, though a disastrous decision nearly robbed him of it.

Ohm, who was born on March 16, 1789 in Erlangen, Bavaria, was the son of a self-educated locksmith. Ohm's father had a great interest in science, which he conveyed to his son. Ohm went on to study at the University of Erlangen in 1805, but left in the following year to become a teacher in Switzerland. He returned to the university in 1811 and received his Ph.D. Ohm's goal in life was to receive a university appointment. Unfortunately, his mathematical talents were not appreciated by academia, and he ended up teaching at the Erlangen "gymnasium" (secondary school).

Still determined to make an impression and receive an appointment, Ohm decided that producing important research work would better his situation. Knowing of the pioneering work of Alessandro Volta, Ohm became interested in studying electricity. Because he was unable to afford to purchase equipment with which to experiment, Ohm had to build his own.

Borrowing from the work of Jean-Baptiste-Joseph Fourier, who had learned that the flow of heat between two points depended on the temperature difference and the material conducting the heat, Ohm applied the concept to the flow of electricity through various electric conductors.

Using wires of differing length and diameter, Ohm discovered that a long, thick wire passed less current than a short, thin wire. This established a relationship between electric resistance, electric potential (electromotive force) and current flow.

In 1827 Ohm issued his "law," stating that the amount of current passing through a wire was inversely proportional to the length and directly proportional to the thickness of a wire. Henry Cavendish had discovered the same relationship nearly fifty years earlier, but neglected to publish the information. Ohm went a step beyond, stating the relationship in mathematical terms: V = IR (the voltage of the current is equal to the current in the circuit times the resistance); doubling the voltage doubles the current, and doubling resistance halves the current. On the other hand, conductance (noted with the letter G) is expressed by two equations: G = I/R and I = GV. Ohm's Law made it possible for scientists to calculate the amount of current, voltage, and resistance in circuitry, establishing the science of electrical engineering. This discovery was Ohm's crowning moment, and he felt certain he would attain his appointment.

Unfortunately, Ohm made a disastrous decision when he published his research: He stressed the mathematical theory behind his work, glossing over the experimental studies. German scientists proceeded to ignore Ohm's equations, believing that mathematics were irrelevant to understanding nature. Ohm received so much ridicule, he not only forfeited an appointment but was also forced to resign the modest teaching position he had at the secondary school.

Ohm spent the next six years in disappointment and poverty. Fortunately his research had made its way to England, where it was fully appreciated. To his delight he began receiving numerous letters of congratulation. He received the Copley Medal in 1841, and was elected to the Royal Society in 1842. In 1843 British scientist Charles Wheatstone credited Ohm for having influenced his own work.

This foreign acclaim began to make an impression on the German scientists, who finally realized the extent of Ohm's discovery. At last, in 1849, Ohm was appointed a professor at the University of Munich, a position he held for the remaining five years of his life. Ohm died at the age of 67 on July 6, 1854.

William Thomson (Lord Kelvin) recognized Ohm's contribution by dubbing the unit of resistance the "ohm" and its reciprocal, the unit of conductance, the "mho" (Ohm's name spelled backward).