General video · Level B1 - Part 2

How do batteries work

Hi Doug. Hi Wayland.

Level: B1 · 91 sentences

Transcript

  1. Hi Doug.
  2. Hi Wayland.
  3. I have a question for you.
  4. How do batteries work?
  5. That's a great question.
  6. Well, believe it or not, the answer to this question involves a story about frog legs.
  7. Yeah, you heard me right, frog legs.
  8. Now, some people prepare and eat the legs of frogs,
  9. just like some people eat chicken legs.
  10. But one scientist by the last name of Galvani
  11. had a dead frog in his laboratory one day.
  12. Not because he was going to eat it,
  13. but because he was getting ready to study it.
  14. Galvani was really interested in figuring out how people's bodies work.
  15. Things like muscles and organs.
  16. At that time, this was a few hundred years ago,
  17. nobody knew yet how exactly people or animals move their muscles.
  18. It's hard to see how muscles work from the outside of an animal's body,
  19. so it can help to look inside.
  20. If an animal dies, scientists can do an operation like a doctor.
  21. This is what's called a dissection.
  22. So Galvani had prepared the frog's legs
  23. so that he could dissect them and study the muscles.
  24. Because he didn't want the frog's legs to rot,
  25. he had soaked them in some salt water overnight.
  26. He got one out, put it in his dissection pan, and then,
  27. as he started to cut it with his scalpel,
  28. something amazing happened.
  29. The leg suddenly began to twitch and jump.
  30. Now obviously, this was extremely surprising.
  31. The frog, after all, was dead.
  32. Its legs shouldn't have been able to move.
  33. Galvani got so excited.
  34. He felt that he had discovered some kind of special power within the frog's muscles.
  35. He thought he must be so close to unlocking the secret of how animals move their muscles.
  36. Well, news of Galvani's discovery spread fast among all the scientists living at that time.
  37. Lots of them were excited to see if they could unlock the secret of how animals move.
  38. One of those scientists, a scientist by the last name of Volta,
  39. found something even more surprising than Galvani.
  40. As Volta tried to repeat Galvani's experiments,
  41. he became convinced that the twitching of the frog's leg
  42. actually had almost nothing to do with the frog
  43. and everything to do with the metal tools that Galvani was using.
  44. For example, Volta found out that in one of Galvani's experiments,
  45. the frog's leg would only twitch when it was being touched by two different metals.
  46. You see, Galvani had used a tool containing the metal copper to hold the frog's leg in place,
  47. and Galvani's knife was made of a different kind of metal,
  48. a metal containing iron.
  49. Volta wondered:
  50. what if this special power that Galvani discovered was actually something contained not in frog's muscles,
  51. but in the two different metals?
  52. Using no frog legs at all, Volta took two pieces of metal,
  53. one of copper and one of iron,
  54. just like the metals used in Galvani's experiment.
  55. Then he connected a piece of wire to each metal disk.
  56. When he touched the two wires together,
  57. well, at first nothing happened.
  58. But that's when Volta remembered
  59. there was one other substance involved in Galvani's frog leg experiments:
  60. salt water.
  61. Volta added a little disk of cardboard soaked in salt water
  62. between the pieces of metal.
  63. Suddenly, now when he connected these together,
  64. he could feel a slight shock.
  65. By stacking up little sandwiches of each metal
  66. separated by disks of salt water-soaked cardboard,
  67. Volta discovered that he could increase the strength of the shock.
  68. With enough of these little disks all piled up,
  69. he could even create a spark.
  70. It looked just like he was making a little lightning bolt.
  71. What Volta had just invented was the very first battery.
  72. In fact, to this day, in some languages, like in French,
  73. a battery still goes by the name of Volta's pile.
  74. At the time that the battery was invented,
  75. Volta and others didn't actually know what kinds of things they'd be useful for.
  76. No one had invented anything powered by electricity yet.
  77. But over time, as you can guess, that all changed.
  78. Today, batteries are one of the most useful inventions ever.
  79. Since batteries are a portable form of electricity,
  80. they allow us to power things without having to be anywhere near an electrical outlet.
  81. Without batteries, we'd have no ability to use smartphones, electric cars,
  82. not even flashlights.
  83. Today's batteries may look different from the first battery ever invented,
  84. although some look incredibly similar on the inside.
  85. Either way, all batteries still work the same basic way.
  86. They all use Volta's amazing discovery
  87. that when you sandwich together two different metals between some kind of liquidy solution,
  88. like salt water or acid,
  89. electricity is produced.
  90. That's all for this week's question.
  91. Thanks, Waylon, for asking it.