- Most of us who've studied
basic physics or electronics have studied Ohm's Law, but did you know that when
Ohm made his law in 1827, it was so widely hated that
he basically lost his job? I'm gonna give a little background on Ohm, how he made his equation with the simple equipment
available at the time, why it was so widely hated, and how it eventually became accepted in the scientific community. Ready? Let's go. ♪ Electricity, electricity ♪ ♪ Electricity, electricity ♪ Georg Simon Ohm was born
in 1787, in Bavaria, and was the oldest of
three children out of seven who survived to adulthood. He was the son of working-class people. His father was a self-educated locksmith, and his mother was the
daughter of a tailor. His father wished for Ohm
and his younger brother to be locksmiths, and
join the family business. However, his father loved mathematics and thought his sons would have
an advantage in their field if they got more mathematics
education in school. Therefore, unusually for sons
of tradesman at the time, both Georg and his younger
brother, Martin Ohm, went to high school or gymnasium. In 1804, when Georg
was about 16 years old, and his brother about 14, a local math professor was so
impressed about what he heard about their mathematical abilities that he wrote to their father that the Ohm brothers were so talented that they would soon, quote, "emulate the brothers Bernoulli". I think he's referencing
Jacob and Johann Bernoulli who were Swiss mathematical scientists famous for their influence
on Bernoulli numbers, infinitesimal calculus, and more. Georg Ohm's father was so
impressed with this letter that he agreed to let
his sons go to college and end the generational
business of locksmithing. Georg Ohm's younger brother eventually became a
prominent mathematician. It was after this letter that Georg Ohm decided to go to college at the University of Erlangen, but he left after 18 months,
as he ran low on funds, so he went to Switzerland
to become a math tutor. It took Ohm five more
years to get his degree, and a further seven years
after that, to 1817, for Ohm to get a permanent position as a math professor and physics teacher at a respected high school called the Great Gymnasium of Cologne. Then, in July of 1820, a Danish scientist and philosopher named Hans Christian Oersted, discovered that current in a wire could move a magnet on a compass, the first discovery of a relationship between electricity and magnetism. One of the important consequences
of Oersted's discovery is it allowed scientists
to use a force on a magnet to determine the direction
and the intensity of the current in a wire. In 1825, Ohm decided to
systematically use this fact to study how the length of metals would change the current in a wire. Ohm said that part of the
reason he chose this topic is he thought it wasn't
particularly popular in Germany, and therefore he wouldn't
have a lot of competition. To measure the current, Ohm had a magnetized needle
suspended over a wire, and then used a tension measuring machine, first invented by Charles Coulomb to measure the electric force, to measure the force between
the wire and the magnet. As Ohm knew his battery had current that would quickly dissipate over time, he created the standard conductor, which was a short and thick piece of metal that he alternated with the pieces he was experimenting with. He then took the average
value of the standard force from the standard conductor as the average value of the force from the current and from the battery, and then measured how much that changed when a test sample was used. In this convoluted way, Ohm
found the complicated equation that he admitted didn't
work well for long wires, but it was a start. He clearly demonstrated
that the longer wires had less current in them. Ohm's next experiment was
conducted in a similar manner with wires of different materials, and thus determined what
is called the conductivity of different materials
compared to each other. It was at this point that
Ohm's former professor, the one who said he and his brother could have been like
the brothers Bernoulli, suggested he might have better luck with something called a
thermocouple as his voltage source, as it is by far more steady. The thermocouple had been discovered five years before, in 1821, when a German physicist named
Thomas Seebeck discovered that if two metals were soldered together and kept at a temperature difference, and then the ends were
connected to a wire, the wire would cause a magnet to turn. Seebeck thought it was a magnetic effect as it caused the magnet to turn, but within a year, Hans Christian Oersted, the same man who discovered
the electromagnetic effect in 1820 suggested that the temperature difference with the two metals was creating a voltage which was creating a current in the wire, which was moving the magnet, and called this a thermoelectric effect, a name we still use to this day. Then, in 1824, Andre-Marie Ampere and his friend, Antoine Becquerel found that the tension of the thermocouple was a function of the
temperature difference. In 1826, Ohm tried a thermocouple with the hot end under boiling water and the cold in ice water, and found to his delight that the current was steady
and strong for over 30 minutes. Ohm then repeated his first
experiment with the thermocouple and measured the magnetic
force from the wire for eight wires of different lengths. Ohm then found that the
strength of magnetic action, i.e., the current, decreased with length X, according to the
equation: a over b plus x. Ohm instantly was quite sure
that the values of a and b depended in some way on the resistance of the other part of the circuit, and what he called the exciting force, although he needed more experiments to determine their dependence. He then wisely redid the experiment with a reduced temperature difference, and therefore, a reduced
exciting force or tension, or what we now call voltage. In this case, as he varied
the length of the wire, the strength of magnetic action also varied by the same equation where the numerator, a, was much reduced, but b was basically the same. In other words, it seemed to Ohm that the current in the wire was related to a simple fraction, where the numerator had to do with the strength of the
battery or the thermocouple, and the denominator had to do
with the length of the wires, or what Ohm called the resistance length. Ohm was quite happy with his conclusions, but felt they lacked
mathematical derivations, and he wanted to model his mathematics after a book on heat flow written by a mathematician
called Joseph Fourier. Anyway, he asked for a
year off to work on this, and by 1827, published a small book called "The Galvanic Circuit
Investigated Mathematically". The book was not a
success, to put it mildly. Critics called it "A
web of naked fancies", and "The result of an incurable delusion whose sole effort is to detract
from the dignity of nature". It is worthwhile to
delve into why this book produced such negative reactions. First, his book was very
mathematically complex and the ideas were not expressed well. For example, a translator of Ohm's book written in 1891 added many sections from other
scientists' papers and books that explain it better so that the reader could have
a chance of understanding what Ohm meant. Secondly, Ohm's conclusion
fell in opposition to what was considered
established fact by the 1820s, namely, they thought that
the current in the wire was independent of the
voltage or the tension of the battery or the thermocouple. This all started with an experiment conducted by Andre-Marie Ampere in 1820. Ampere wanted to see the relationship between the strength of the
battery and the current, so he measured the magnetic deflection from a wire connected to a battery, and then redid the experiment with several batteries in series, and found to his surprise that to the accuracy of the compass, the magnetic deflection,
and therefore the current, was the same. As multiple batteries in
series caused a bigger shock, it was clear that these extra batteries had more tension in them, and therefore Ampere concluded that the tension was
independent of the current. However, what Ampere and other
contemporaries didn't know was that batteries have something
called internal resistance and that their batteries had
very high internal resistance. By using several batteries, you do get more tension or voltage, but you also get more internal resistance. As the total resistance in this experiment is mostly from the internal resistance, increasing the number of batteries increases the total resistance almost as much as it
increases the voltage, and therefore, the current only
increases by a minute amount too small to be observed
by their simple setups. Thirdly, Ohm was talking
about tension in a new way. At the time, tension came from the battery or the thermocouple. One did not talk about the tension, or what we call the potential difference between two points in a circuit. This is a difficult concept
to understand and appreciate, and like I said before, Ohm was brilliant enough
to come up with it, but not brilliant enough to explain it in a very understandable method. Fourthly, and most damaging, Ohm's work was opposed by a
scientist named George Pohl. Pohl had just published his own work on the science of circuits and was, not surprisingly,
not too favorable to Ohm, and Pohl called Ohm's results
"an unmistakable failure", and convinced the German
Minister of Education that, quote, "A physicist
who professes such heresies was unworthy to teach science." Ohm was devastated,
especially with the thought that his superiors at the gymnasium were offended by his work, and he declared it was impossible for him to retain this position, and quit, full of, as a biographer put it, mortification and grief. Ohm then struggled to
find another position, and mostly made a living as
a tutor to a military school. It took Ohm until 1833 for
Ohm to find a new position as a professor at a Polytechnic
School in Nuremberg. Ohm's work first became truly promoted by mainstream scientists
in England, not in Germany. See, in the 1830s, an English shoemaker who had invented the electromagnet, named William Sturgeon, got in a fight with the people at the Royal Society of London. In mid-1836, Sturgeon
started his own newspaper where he published a
description of a motor he made that he claimed was very powerful "upon the same scale we
see pieces of machinery put in motion by the large
models of steam engines." Soon many English tinkerers were trying to make
their own electric motor or other electric devices, and scouring Sturgeon's
magazine for advice. In 1837, Sturgeon published
a translation of an article written by a Russian
architect living in Germany, named Moritz Jacobi, who had invented his own
motor three years earlier, which was clearly superior to Sturgeon's. In addition, Jacobi, whose
brother was a mathematician, was a fan of Ohm, and wrote a paper that his motor was derived
from the theories of Ohm, as, quote, 'The theory
established by Mr. Ohm offers so much simplicity,
and agrees so well with all the phenomena of the voltaic pile that I have not hesitated to adopt it." Note that even though Jacobi
published this article in France, and in Germany, and in Russia, it didn't attract very much attention. However, the translation in
English in Sturgeon's paper due to the fact that
Sturgeon totally overstated how powerful his motor was, caused many people in England, at least, the readers and the
contributors to his magazine, to start using Ohm's Law,
and refer to Ohm's Law, and to Ohm's idea of resistance, though it was still generally ignored by most established scientists, especially at the Royal Society. Luckily, there was an engineer
named Charles Wheatstone who bridged the gap between the tinkerers who read
William Sturgeon's magazine and the scientists at the Royal Society. Wheatstone first became
interested in science in the study of sending acoustic signals. When he was just a teenager,
he invented an enchanted lyre as a gimmick to attract attention
to his uncle's music shop, where he caused the
musical instrument to ring by playing a piano hidden in another room that was connected with wires. Over the years, Wheatstone continued to study sound propagation, and he invented several
musical instruments. In 1834, Wheatstone demonstrated a method of measuring the speed
of electricity in a wire, caused him to be quite
famous in scientific circles. He was instantly hired as a professor at King's College in London, although he almost never gave lectures as he had a terrible
fear of public speaking. Then, in February of 1837, a
soldier named William Cooke met with Wheatstone for help with an idea of
an electric telegraph. They soon formed a partnership which made both of them quite famous. Wheatstone read Jacobi's paper about Ohm, and he, too, became an Ohm super fan. Then in 1838, the British Association for
the Advancement of Science decided to allocate 100 pounds for translating and
publishing scientific memoirs. Wheatstone was on the committee, and with his help and encouragement, by 1841, they had translated
and published Ohm's work. Suddenly, the scientific establishment started to learn about
Ohm and become Ohm fans. That year, Ohm was awarded England's Royal Society's
highest honor, the Copley Medal, for his "researches into the
laws of electric currents". Meanwhile, Wheatstone continued
to push for Ohm's theories, and in 1842, when he asked
his friend, Ida Lovelace, to make a better
translation of Ohm's work, and in 1843, when he introduced what is now called the Wheatstone bridge, where Wheatstone said that, quote, "the instrument and processes
I'm about to describe being all founded on the principle established by Ohm in his
theory of the voltaic current, and this beautiful and
comprehensive theory". Ohm felt indebted to the
people at the Royal Society, apparently, he didn't
know about Wheatstone, and dedicated a 1849
book on molecular physics to the Royal Society, as he said their support
gave him the courage "which had previously been softened by disheartening treatment to renewed effort in
the fields of science." Ohm hoped this book would be the first of three, or maybe even four
books on molecular physics. However, he then realized that his ideas had already been published, and he gave up on the whole project. Ohm died in July of
1854, at the age of 65, from an attack of apoplexy. Eventually, Ohm's results are
simply known as Ohm's Law, and it is written as voltage equals resistance times current. In 1861, the British Association for
the Advancement of Science proposed the standard unit for resistance to be Ohma, in Ohm's honor, which was shortened to Ohms in 1867. As capital O looks like a zero, the unit of Ohms were given
the Greek letter omega, as omega starts with the letter O, and we use this nomenclature to this day. As a side note, I was amused to learn that conductivity, or the
inverse of resistance, how easy it is for electricity
to flow through a material, is measured in mhos, in reverse
or upside down Ohm's honor. So that was a little biography of Ohm, and how he discovered his law, and how it eventually
ended up being accepted in scientific communities. Now, I wanna talk about
someone besides Wheatstone who was inspired by Sturgeon's magazine and the description of Ohm's Law. Although he was just a young beer brewer, he eventually used those
ideas to change the world. His name, James Prescott
Joule, and his story is next time on The Lightening Tamers. Thanks for watching my video. Hope you enjoy it. Fun fact, Charles Wheatstone is mentioned in another one of my videos, the one about how Faraday discovered that light was a electromagnetic wave. You should go check it out. It's kind of fun to see him pop up there, and his fear of public speaking. I will put a link down below. Speaking of links, big
thank you to my patrons. Thank you, patrons. If you wanna be thanked too, there's a link down
below, you can join them. Please tell me in the comments below, do you want me to make a
video on Wheatstone bridge, a little bit more detail
about Wheatstone, or skip it? Okay, tell me what you think. Stay safe out there. Bye. Secondly, Ohm's conclusion
fell in opposition to what, er, established
in er, du, du, du, du, du.
