- How did little pieces of gold
lead to the first rules of electricity
and why is it only half correct?
What was correct and what was incorrect?
Well, I'll tell you,
and along the way,
I'll tell you how static electricity works,
why it doesn't work on humid days
and why it often flows away and confuses us.
Ready?
Let's go.
♪ Electricity, electricity ♪
In 1731, an Englishman named Stephen Gray
published a series of letters in the Royal Society
about how electricity conducts.
It was almost universally ignored.
Everyone was fascinated instead
studying Newton's revolutionary ideas about gravity
and forces of the distance.
However, it was read by a 33-year-old wealthy nobleman
named Charles Francois de Cisternay du Fay.
Du Fay came from a long line of diplomats and soldiers.
In fact, he became a soldier at the tender age of 14,
but retired early to follow his true love,
which was science.
When Du Fay read that article from Stephen Gray,
that electricity could flow,
Du Fay wondered if every material could become electric
and we just didn't notice it,
because sometimes the electricity would flow
into the ground.
See at the time, electric meant that small objects
would be attracted to it if it was rubbed.
People thought that metals weren't electrics,
because if you rubbed them, nothing would stick to them.
Du Fay thought, maybe what was happening
was when you rubbed them,
you were creating an electric charge,
but it just flowed through your hand and into the ground.
So you never noticed it.
Therefore, he rubbed a metal object
without touching it with his bare hand
and put it on an insulating stand
or a stand that would not let the electrical fire flow out.
He used wax, I'm using a cotton pot holder.
This way metal objects could attract feathers,
just like glass or wax could.
In this manner, Du Fay found that every solid object
he played with would attract objects if it was rubbed.
In other words, he determined that electricity
is in all things, it's everywhere.
Du Fay then read all the literature available
about electric forces, which didn't take long.
He found that 65 years earlier,
a German man named Otto von Guericke
had found that after feathers were electrically attracted
to a smelly ball of sulfur,
the feathers would fall off and be repulsed by the ball.
Du Fay tried it with other less smelly objects
and found that if he waited,
all objects would electrically attract small objects
and then after a time, electrically repel the same objects.
This is when Du Fay started to play
with little pieces of gold.
You see, if they have the money
scientists love to experiment with gold.
It is conductive, but also so malleable
that you can pound it super thin and make it light,
even lighter than feathers.
Du Fay of course, had the money to play with gold.
When he charged up his glass tube
and put a piece of gold near it,
the gold would jump up to the glass tube,
and then bounce off it and stick to the floor,
then it would jump back up to the tube.
On a dry day, he could make the gold dance.
This is where Du Fay came up with
his first simple principle about how electricity works.
And we still think it is correct 280 years later.
In his own words,
"Electric bodies attract all those that are not so,
and repel them as soon as they become electric
by contact with the electric body."
In other words,
the neutral feather or piece of gold or aluminum foil ball
was attracted to the charged rod.
When it touched the glass tube,
it gets some of the charge and was repelled.
Then when it touched the ground,
it lost its charge and became neutral
and could be attracted again.
This explains why electrical experiments
only work well on dry days.
On humid days, the water droplets
are attracted to the charged objects,
and then once in contact,
they gained some of the charge and are repelled.
This happens with multiple water droplets
until the charged object loses all of its charge
and no electrical experiments can be conducted.
Du Fay had an ingenious method for validating his theory.
He took two tubes and rubbed them separately.
He then took a piece of gold foil
and put it near one of his tubes
and watched it be attracted and repelled.
His theory was it was repelled,
because it took some of the charge,
therefore, he expected the gold foil to be repelled
by the second tube.
Instead, he was flabbergasted to see that the gold foil
was attracted to the second tube instead,
and then after a little while,
repelled by the second tube and attracted to the first tube.
You can see this process more easily,
as well as cheaply with feathers instead of gold foil.
Notice that the feather is attracted to one tube,
and then is attracted to the second tube.
Du Fay decided that this was happening,
because the tubes were made of different materials.
One was made of glass and the other of sealing wax.
In other words, there's more than one type of electricity.
He named one type of electricity,
vitreuos electricity for glass like,
and one type resinous electricity for wax like.
After exhaustive experimentation,
Du Faye found that every object would fit neatly
into one of these two categories.
He also found that objects have the same charge,
they would repel, and different charges they would attract.
Du Fay had created the basic law of electricity,
opposites attract, like repel,
and charged objects attract neutral.
That is completely correct.
So what did he get wrong?
Well, it's a subtle mistake, but an important one.
Du Fay thought he was creating electricity.
He thought if you rubbed glass object,
you're creating glass electricity,
if you rubbed wax object, you were creating wax electricity.
That isn't true.
You're not creating electricity, you are moving electricity.
When you rub a glass object with say your hand,
the electrons are moving from your hand
into the glass object,
leaving the glass object with a negative charge
and your hand with a positive charge.
When he rubbed a wax object with his hand,
the wax object lost electrons,
leaving it with a positive charge
and his hand with a negative charge.
Electricity always has symmetry.
However, because the electricity in your body
very easily flows into the ground
it's sometimes hard to see that it has that symmetry.
Du Fay wrote 17 additional papers about electricity
over the next five years.
Who knows how many more he would have written
if he hadn't died at age 41 in 1739 from smallpox.
Now that the wealthy scientists had deemed electricity
worthy of study,
more and more people throughout Europe
started to study electricity.
The most influential, not to mention the most flamboyant
was a German wizard named Matthais Bose.
Bose took the rigorous studies of Du Fay
and combined it with the static electricity machine
of a man named Hauksbee
to make the most dramatic electrical experiments
the world had ever seen.
He actually started an electricity craze throughout Europe
and his story, not to mention his bad poetry,
are next time on "The Secret History of Electricity".
♪ Electricity, electricity ♪
Thanks for watching my video.
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Have a good day.
(upbeat music)