When Ohm got it wrong
Keith Wilson - Electrical Engineer
German physicist and mathematician Georg Simon Ohm is well known today for the law that bears his name, which is now ubiquitous in the world of electricity and electronics. But how did he devise his famous law? Well, that was quite a winding road, even for a genius academic like Ohm!
The concept of galvanic fluid (or electrical current as we know it today) existed since the early 1800’s but until Ohm, it remained a mysterious force that even great minds such as Volta and Oersted struggled to tackle experimentally.
Ohm, however, saw the possibility of combining Volta’s new galvanic battery with a galvanoscope to study the nature of the electrical current flow. Ohm wanted to find the relationship between applied potential, the length of the conductor and the deflection of the galvanoscope needle.
His solution was to connect the galvanoscope directly to the battery and then note the position of the needle, which gave him a reference reading. He then inserted a wire of known composition and length into the circuit and noted the new position of the needle. As would be expected, the needle showed a smaller deflection – in modern terms, the current in the circuit was reduced by the resistance of the wire. Ohm repeated his experiment with many different samples of wire.
Excited by his findings, he rushed ahead to publish his research in a paper called very simply: “Preliminary Notice of the Law According to Which Metals Conduct Contact Electricity”. Unfortunately for him, the equation he published was incorrect as it stated that v = m log(1+x/r) where v is the decrease in the needle deflection, x represents the length of the conductor, r represents the resistivity of the conducting material and m stands for the applied potential.
By the time Ohm realised he had made a mistake, his paper had already gone to print and all he could do was publish a letter promising more tests to put things right. Ohm’s approach infuriated the scientific community and even the great philosopher Hegel spoke out against him!
Ohm did, of course, refine his theory and two more papers followed suit, where he looked at galvanic batteries in more detail. He thought that his final piece of research published under the title “The Galvanic Battery Treated Mathematically” would be enough to gain the approbation of his peers. Alas, they were still unimpressed with his law of electrical conduction.
To them, his equation seemed far too simple to be true. Secondly, Ohm’s retractions and multiple variants had convinced his peers that he was not rigorous in his work, and that he was only a dilettante.
Utterly disheartened, Ohm retired from the scientific community, only to receive recognition sixteen years later when Pouillet’s research proved Ohm’s later theories were absolutely right. As a result, in 1841, the British Royal Society made some small recompense to Ohm by awarding him a medal for “the most conspicuous discovery in the domain of exact investigation”.
