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  • You probably know the feeling.

  • Your phone utters its final plaintive "bleep"

  • and cuts out in the middle of your call.

  • In that moment, you may feel more like throwing your battery across the room

  • than singing its praises,

  • but batteries are a triumph of science.

  • They allow smartphones and other technologies to exist

  • without anchoring us to an infernal tangle of power cables.

  • Yet even the best batteries will diminish daily,

  • slowly losing capacity until they finally die.

  • So why does this happen,

  • and how do our batteries even store so much charge in the first place?

  • It all started in the 1780s with two Italian scientists,

  • Luigi Galvani and Alessandro Volta,

  • and a frog.

  • Legend has it that as Galvani was studying a frog's leg,

  • he brushed a metal instrument up against one of its nerves,

  • making the leg muscles jerk.

  • Galvani called this animal electricity,

  • believing that a type of electricity was stored in the very stuff of life.

  • But Volta disagreed,

  • arguing that it was the metal itself that made the leg twitch.

  • The debate was eventually settled with Volta's groundbreaking experiment.

  • He tested his idea with a stack of alternating layers of zinc and copper,

  • separated by paper or cloth soaked in a salt water solution.

  • What happened in Volta's cell is something chemists now call oxidation and reduction.

  • The zinc oxidizes, which means it loses electrons,

  • which are, in turn, gained by the ions in the water in a process called reduction,

  • producing hydrogen gas.

  • Volta would have been shocked to learn that last bit.

  • He thought the reaction was happening in the copper,

  • rather than the solution.

  • None the less, we honor Volta's discovery today

  • by naming our standard unit of electric potential "the volt."

  • This oxidation-reduction cycle creates a flow of electrons between two substances

  • and if you hook a lightbulb or vacuum cleaner up between the two,

  • you'll give it power.

  • Since the 1700s, scientists have improved on Volta's design.

  • They've replaced the chemical solution with dry cells filled with chemical paste,

  • but the principle is the same.

  • A metal oxidizes, sending electrons to do some work

  • before they are regained by a substance being reduced.

  • But any battery has a finite supply of metal,

  • and once most of it has oxidized, the battery dies.

  • So rechargeable batteries give us a temporary solution to this problem

  • by making the oxidation-reduction process reversible.

  • Electrons can flow back in the opposite direction

  • with the application of electricity.

  • Plugging in a charger draws the electricity from a wall outlet

  • that drives the reaction to regenerate the metal,

  • making more electrons available for oxidation the next time you need them.

  • But even rechargeable batteries don't last forever.

  • Over time, the repetition of this process causes imperfections

  • and irregularities in the metal's surface that prevent it from oxidizing properly.

  • The electrons are no longer available to flow through a circuit

  • and the battery dies.

  • Some everyday rechargeable batteries

  • will die after only hundreds of discharge-recharge cycles,

  • while newer, advanced batteries can survive and function for thousands.

  • Batteries of the future may be light, thin sheets

  • that operate on the principles of quantum physics

  • and last for hundreds of thousands of charge cycles.

  • But until scientists find a way to take advantage of motion

  • to recharge your cell battery, like cars do,

  • or fit solar panels somewhere on your device,

  • plugging your charger into the wall,

  • rather than expending one battery to charge another

  • is your best bet to forestall that fatal "bleep."

You probably know the feeling.

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B2 TED-Ed volta battery oxidation metal reduction

【TED-Ed】How batteries work - Adam Jacobson

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    稲葉白兎 posted on 2015/05/22
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