Placeholder Image

Subtitles section Play video

  • (Music)

  • I'm going to try to shine a historical light on our language,

  • and tell you a story about the electric vocabulary.

  • It all begins over 2,600 years ago.

  • An ancient Greek, called Thales of Miletus,

  • is thought to be the first person to observe

  • what we would today call electrical phenomena.

  • He discovered that a piece of amber, when rubbed with fur,

  • could pick up small pieces of straw

  • In Thales' language, amber was called electron.

  • For a long time, that was pretty much all anybody knew about the subject.

  • And nature had to wait around 2,200 years

  • before any new investigations were made

  • into amber's properties.

  • William Gilbert, a 17th century English scientist,

  • discovered that with a careful experimentation,

  • a number of other materials could display the attractive properties

  • of amber.

  • He also found that they could attract objects besides straw.

  • Gilbert named these amber-like objects

  • after the Greek for amber.

  • He called them "electrics."

  • About 40 years later, in nearby Norwich,

  • Sir Thomas Browne carried out some more experiments.

  • He didn't figure out anything different from William Gilbert,

  • yet the way he described the experiments

  • coined the word we use all the time.

  • The way he saw it, when you rub, say, a crystal with a cloth,

  • it becomes an electric object.

  • And just as we speak of elastic objects,

  • and say they possess the property of elasticity,

  • electric objects possess the property of electricity.

  • The 18th century French physicist

  • Charles du Fay was the next person to make an important new discovery.

  • He found that almost any object, except for metals and fluids,

  • could be turned electric

  • after subjecting them to a combination of heating and rubbing.

  • In addition, he found that when two electrics are place near each other,

  • they sometimes attract and sometimes repel.

  • With this extra knowledge,

  • du Fay found that there were two distinct groups of electrics.

  • Any two objects from the same group

  • will always repel,

  • while a pair of one from each group

  • will always attract.

  • Despite these new discoveries,

  • du Fay's descriptions of the physics are all lost to history.

  • Instead, it is the vocabulary of a charismatic young American

  • that we still remember and use to this day.

  • Benjamin Franklin heard of the work going on in Europe

  • and started his own playful experiments.

  • He quickly learned how to make electric devices

  • that would de-electrify by producing very large sparks.

  • Keen on mischievous pranks,

  • Franklin would often shock his friends with these machines.

  • As he built more effective devices,

  • he likened the act of electrifying

  • and de-electrifying to charging and discharging weaponry.

  • It didn't take long for Franklin and others to realize

  • that it was possible to link these weapons of mischief together.

  • Franklin, continuing with the metaphor,

  • likened this grouping to cannons on a ship.

  • The gun deck on a military vessel

  • fired their cannons simultaneously, in a battery

  • Similarly, this electric battery

  • would discharge all at the same time,

  • causing large sparks.

  • This new technology raised an interesting question:

  • Was a lightning cloud just a large electrical battery?

  • Franklin's description of all this was as follows:

  • He supposed that there was a substance

  • he called the "electrical fluid" that is common to all things.

  • If, say, a person rubs a glass tube,

  • this rubbing, or charging, causes a flow of this fluid,

  • or an electrical current, to move from the person to the glass.

  • Both the person and the tube become "electrics" as a result.

  • Normally, if the person was standing on the ground,

  • their electrical fluid would return to normal,

  • with an exchange from the common stock of the Earth,

  • as Franklin called it.

  • Standing on something like a wax block

  • can cut off this supply.

  • Franklin said that an object with an excess of this fluid

  • was positively charged,

  • and something lacking this fluid was negatively charged.

  • When objects touch, or are near each other,

  • the electrical fluid can flow between them

  • until they reach a balance.

  • The bigger the difference in the fluid between the two objects,

  • the larger the distance the fluid can jump,

  • causing sparks in the air.

  • And it is the material of the object

  • that determines if it gains or loses electrical fluid

  • during charging.

  • These are du Fay's two groups of electrics.

  • You might have heard the phrase, "Opposite charges attract,

  • like charges repel."

  • That's why.

  • For the next 150 years,

  • Franklin's theory was used to develop

  • many more ideas and discoveries,

  • all using the vocabulary he invented.

  • this scientific inquiry brought forth technological advances

  • and eventually, scientists were able to take a closer look

  • at the electric fluid itself.

  • In 1897, J.J. Thomson, working in Cambridge, England,

  • discovered that the electrical fluid

  • is actually made up of small particles

  • named by the physicist George Stoney

  • as electrons.

  • And so we return to the ancient Greek word for amber,

  • where our story began.

  • However, there's an epilogue to this tale.

  • It was discovered that these electrons flow

  • in the opposite direction to what Franklin supposed.

  • Therefore, objects that are positively charged

  • don't have an excess of electrical fluid,

  • they actually lack electrons.

  • Yet, instead of relabeling everything the other way around,

  • people have decided to hold on to Franklin's vocabulary

  • as a matter of habit and convention.

  • While acknowledging the discovery of electrons,

  • it kept Franklin's flow of electrical fluid,

  • renaming it "conventional current."

  • The electron has become the salmon of electricity,

  • swimming upstream in a ghostly river

  • of conventional current.

  • This can be understandably confusing for many people

  • who aren't familiar with the history of these ideas.

  • And so I hope,

  • with this short story about the electric vocabulary,

  • you will be able to see through the accident and whimsy of this subject

  • and can gain a clearer understanding

  • of the physics of electrical phenomena.

(Music)

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B1 TED-Ed fluid franklin electrical amber electric

【TED-Ed】Electric vocabulary - James Sheils

  • 1167 115
    稲葉白兎 posted on 2014/12/29
Video vocabulary