- 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 ♪
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.
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