Electric Vocabulary

653,025 views ・ 2012-07-16

TED-Ed


Please double-click on the English subtitles below to play the video.

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I'm going to try to shine a historical light on our language,
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and tell you a story about the electric vocabulary.
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It all begins over 2,600 years ago.
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An ancient Greek, called Thales of Miletus,
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is thought to be the first person to observe
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what we would today call electrical phenomena.
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He discovered that a piece of amber, when rubbed with fur,
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could pick up small pieces of straw.
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In Thales's language, amber was called "electron."
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For a long time, that was pretty much all anybody knew about the subject.
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And nature had to wait around 2,200 years
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before any new investigations were made into amber's properties.
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William Gilbert, a 17th-century English scientist,
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discovered that with a careful experimentation,
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a number of other materials
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could display the attractive properties of amber.
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He also found that they could attract objects besides straw.
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Gilbert named these amberlike objects
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after the Greek for amber.
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He called them "electrics."
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About 40 years later, in nearby Norwich,
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Sir Thomas Browne carried out similar experiments.
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He didn't figure out anything different from William Gilbert,
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yet the way he described the experiments
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coined the word we use all the time.
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The way he saw it, when you rub, say, a crystal with a cloth,
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it becomes an electric object.
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And just as we speak of elastic objects,
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and say they possess the property of elasticity,
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electric objects possess the property of electricity.
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The 18th-century French physicist Charles Du Fay
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was the next person to make an important new discovery.
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He found that almost any object, except for metals and fluids,
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could be turned electric
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after subjecting them to a combination of heating and rubbing.
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In addition, he found that when two electrics are place near each other,
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they sometimes attract, and sometimes repel.
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With this extra knowledge,
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Du Fay found that there were two distinct groups of electrics.
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Any two objects from the same group will always repel,
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while a pair of one from each group will always attract.
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Despite these new discoveries,
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Du Fay's descriptions of the physics are all lost to history.
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Instead, it is the vocabulary of a charismatic young American
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that we still remember and use to this day.
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Benjamin Franklin heard of the work going on in Europe,
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and started his own playful experiments.
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He quickly learned how to make electric devices
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that would De-electrify by producing very large sparks.
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Keen on mischievous pranks,
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Franklin would often shock his friends with these machines.
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As he built more effective devices,
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he likened the act of electrifying and De-electrifying
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to charging and discharging weaponry.
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It didn't take long for Franklin and others to realize
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that it was possible to link these weapons of mischief together.
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Franklin, continuing with the metaphor,
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likened this grouping to cannons on a ship.
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The gun deck on a military vessel
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fired their cannons simultaneously, in a battery.
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Similarly, this electric battery,
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would discharge all at the same time,
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causing large sparks.
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This new technology raised an interesting question:
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Was a lightning cloud just a large electrical battery?
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Franklin's description of all this was as follows:
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he supposed that there is a substance
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he called the electrical fluid, that is common to all things.
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If, say, a person rubs a glass tube,
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this rubbing, or charging, causes a flow of this fluid,
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or an electrical current, to move from the person to the glass.
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Both the person and the tube become electrics as a result.
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Normally, if the person was standing on the ground,
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their electrical fluid would return to normal,
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with an exchange from the common stock of the Earth,
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as Franklin called it.
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Standing on something like a wax block can cut off this supply.
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Franklin said that an object with an excess of this fluid
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was positively charged,
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and something lacking this fluid was negatively charged.
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When objects touch, or are near each other,
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the electrical fluid can flow between them
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until they reach a balance.
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The bigger the difference in the fluid between the two objects,
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the larger the distance the fluid can jump,
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causing sparks in the air.
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And, it is the material of the object
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that determines if it gains or loses electrical fluid
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during charging.
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These are Du Fay's two groups of electrics.
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You might have heard the phrase:
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"Opposite charges attract, like charges repel."
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That's why.
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For the next 150 years,
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Franklin's theory was used to develop
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many more ideas and discoveries,
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all using the vocabulary he invented.
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This scientific inquiry brought forth technological advances
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and eventually, scientists were able to take a closer look
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at the electric fluid itself.
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In 1897, J.J. Thomson, working in Cambridge, England,
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discovered that the electrical fluid is actually made up of small particles
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named by the physicist George Stoney as "electrons."
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And so we return to the ancient Greek word for amber,
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where our story began.
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However, there's an epilogue to this tale.
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It was discovered that these electrons flow
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in the opposite direction to what Franklin supposed.
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Therefore, objects that are positively charged
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don't have an excess of electrical fluid,
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they actually lack electrons.
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Yet, instead of relabeling everything the other way around,
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people have decided to hold on to Franklin's vocabulary
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as a matter of habit and convention.
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While acknowledging the discovery of electrons,
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they kept Franklin's flow of electrical fluid,
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renaming it: conventional current.
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The electron has become the salmon of electricity,
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swimming upstream in a ghostly river of conventional current.
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This can be, understandably, confusing for many people
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who aren't familiar with the history of these ideas.
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And so I hope,
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with this short story about the electric vocabulary,
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you will be able to see
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through the accident and whimsy of this subject
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and can gain a clearer understanding
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of the physics of electrical phenomena.
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