- How did Benjamin Franklin discover about electricity,
and what did he discover about electricity
once he had heard about it?
Well, I'll tell you, and along the way,
I'll tell you about the origin
of positive and negative charges,
the longest standing rule of physics,
a terrifying experiment involving lightning,
and a simple mistake that still plagues us today.
Ready? Let's go.
♪ Electricity, electricity ♪
In 1746, an Englishman named Peter Collinson
read an article about some wonderful
German experiments involving electricity,
like giving electric kisses and electrifying a person
and using a spark from that person
to light alcohol and fire.
Collinson was a Quaker merchant and amateur scientist
who was friends with Benjamin Franklin in Philadelphia.
Yes, that Ben Franklin,
the one who helped write the declaration of independence
and who is frowning on the a hundred dollar bill.
Collinson sent Franklin a copy of the magazine
in a glass tube with a shipment
of other materials for his library.
Franklin was instantly hooked.
Quote, "For my part, I never was before engaged
in any study that so totally engrossed my attention
and my time as this has lately done
and my friends come continuously in crowds to see them.
I have, during some months past,
had little leisure for anything else.
At the time, Franklin was 40 years old,
he had a successful printing shop,
post office and stationary shop,
and only two children to support, 15 year old William
and three-year-old Sally.
In comparison, Franklin was from a family of 17 children,
seven from his father's first wife who died in childbirth
and 10 from Ben's mother who survived
bearing 10 children and raising 17.
Around this time, Franklin found a manager for his business
and felt that he was quote, "Free to having no other tasks
than I should like to give myself,"
with leisure to read, make experiments,
and converse at large with such ingenious
and worthy men as are pleased
to honor me with their acquaintance.
Franklin began writing Collinson,
thanking him for his kind present
and giving him his theories about electricity.
One of the first things he related
after he related how much fun electricity was,
was that electricity seemed to come from
and go to a sharp point.
This was to be vital for the invention of the lightning rod,
which we'll get to in a little bit.
Meanwhile, he built his own electricity machine,
but unlike other machines at the time,
which had one person to spin the wheel
and the separate person to rub the wheel
with their bare hand, Franklin's had a brush
rub against the glass.
Interestingly, you could charge up another person
by putting them on wax and having them
either touch the spinning glass or the brush.
Because of this, Franklin quickly came to the theory,
contrary to all of those beforehand
that you cannot create or destroy charge, only move it.
In other words, all things contain charges,
and when you rub them, you move some of the charges
onto the other object.
And you can either have an excess of charge
or a lack of charge.
This is called conservation of charge,
and it a longest standing rule of physics.
Franklin thought, if you rub glass with wool,
the glass lost electrical fire
and the wool gained electrical fire.
He gave these processes a name that we're stuck with today.
If something has too much electrical fire,
it's charged positively, too little charged negatively,
and just the right amount charged neutrally.
His proof was that if you charged up two people
by having one touch the glass and one touch the brush,
they could give each other a terrible shock.
But after that, they would both be uncharged.
In other words, the glass person got the equal
and opposite charge of the brush person.
It was decidedly a shopkeeper's physics
with all the pluses and minuses like an accountant's ledger.
And it was almost correct.
See, one of the problems is if you see a spark
or experience one, it's impossible to tell
which direction it's going in.
It is just as painful to lose electrons
as it is to gain electrons.
Franklin arbitrarily decided that the positive charges
were the ones that were moving,
took a further 150 years to realize electrical fire
that was moving was really electrons and they are negative.
So when we think electricity flows one way,
it really flows the other way.
Oops, we are still stuck with this mistake today.
If for example, you connect the battery to a light bulb.
We would say that the current flows from positive
to negative when we know what is really going on
is that the tiny negative electrons
are flowing the other way.
Once again, oops.
Still despite that mistake,
Franklin's observation that everything contains charge
and you can only move it, not create it or destroy it,
was a brilliant observation and changed
how people understood electricity
at least for the few people
who read Franklin and understood him.
Meanwhile, Franklin was not only making up
new rules for electricity, he was also having a lot of fun.
He came up with many new ingenious demonstrations
like flying spiders and putting gold leaf
on the side of a book and discharging a Leyden jar across it
so that the gold would sparkle and glow
to amuse his friends and visitors.
He did have a little trouble when he tried
to electrically kill his Turkey for Christmas
and he almost electrocuted himself.
But in general, he seemed to find
electricity endlessly amusing.
While playing with his electricity machine
and trying to electrocute turkeys,
Franklin started to think about lightning.
He became convinced that it was the same as the sparks
he got at home, but on a larger scale.
On November 7th, 1749, Franklin wrote his friend a list
of 12 similarities between sparks and lightning.
On July 29th, 1750, Franklin came up
with a terrifying experiment to test whether lightning
was caused because the clouds were electrified.
He proposed you could put a large iron rod in a tiny house
like a guard house, or would he called sentry box.
He thought if a cloud pass by,
if the clouds were electrified,
then the rod would also be electrified by induction,
moving charges at a distance and could produce sparks.
Notice that despite most layman's impressions at the time,
and even today, Franklin was assuming
that the metal rod would create sparks
because it was near an electrified cloud,
not because it was hit by lightning.
It was this experiment, the soldier in the box one
that thrust Franklin into international fame.
See, in 1749, Collinson decided to publish
Franklin's letters as a book.
When they did, it initially did not do that well in England.
Ever the politician, Franklin realized
that his ideas of moving positive and negative charges
would have an even harder time in France,
as it was contrary to the prevailing theory
created by a Frenchman named
Charles Francois Cisternay Du Fay.
Now Du Fay had died from smallpox in 1739, but his protege,
a man named Nollet seemed unlikely to enjoy Franklin's work.
Therefore, Franklin happened to send it to Nollet's rival,
a pompous man named Buffon.
Buffon had no previous interest in electricity,
but he was delighted to humiliate a rival,
and that story and how it led to the lightning rod,
as well as Franklin's famous kite experiment,
is next time on the secret history of electricity.
♪ Electricity, electricity ♪
Thanks for watching my video.
Please remember to give it a big thumbs up.
I always appreciate that.
Also, if you want to know how the Leyden jar works
and you haven't seen my last video, please check it out.
Thanks and have a good day.
(jazzy music)