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  • Have you ever seen static electricity cause a spark of light?

  • What is that spark?

  • What about lightning,

  • the Northern Lights,

  • or the tail of a comet?

  • All of those things, and many others,

  • in fact 99.9% of the universe, are made of plasma.

  • Plasma is a state of matter

  • drastically different from the more familiar forms.

  • Take ice, for example.

  • Ice, a solid, melts to become water, a liquid,

  • which, when heated, vaporizes into steam, a gas.

  • Continued heating of the steam at a high enough temperature

  • causes the water molecules in it to separate

  • into freely roaming hydrogen and oxygen atoms.

  • With a little more heat, the ionization process occurs

  • and the negatively charged electrons escape the atoms,

  • leaving behind positively charged ions.

  • This mixture of freely roaming negative and positive charges is plasma,

  • and at a high enough temperature, any gas can be made into one.

  • These freely moving charged particles behave very differently

  • from the particles in other types of matter.

  • When a doorknob, a solid, has static electricity on it,

  • it doesn't look or behave any differently.

  • And with the exception of a compass or other magnetic object,

  • we rarely see matter respond to a magnetic field.

  • But put a plasma in an electric field or magnetic field,

  • and you'll get a very different reaction.

  • Because plasmas are charged,

  • electric fields accelerate them,

  • and magnetic fields steer them in circular orbits.

  • And when the particles within plasma collide,

  • or accelerated by electricity or magnetism,

  • light is generated,

  • which is what we see when we look at plasmas

  • like the Aurora Borealis.

  • Plasmas aren't just beautiful, celestial phenomena, though.

  • Imagine a tiny cube made of normal gas with a very high voltage across it.

  • The resulting electric field

  • pushes some of the electrons off the atoms and accelerates them to high speeds

  • causing the ionization of other atoms.

  • Imbedded impurities in the tiny cube of gas

  • cause it to gain and release a precise amount of energy

  • in the form of ultraviolet radiation.

  • Attached to each tiny cube,

  • a fluorescent material glows with a specific color

  • when ultraviolet light at just the right intensity reaches it.

  • Now, make a rectangle out of a million of these tiny cubes,

  • each separately controlled by sophisticated electronics.

  • You may be looking at one now.

  • This is called a plasma TV.

  • Plasmas also have implications for health care.

  • Plasma chemists create highly specific plasmas

  • that can destroy or alter targeted chemicals,

  • thereby killing pathogenic organisms on food or hospital surfaces.

  • Plasmas are all around us,

  • in forms that are both spectacular and practical.

  • And in the future, plasma could be used

  • to permanently rid landfills of their waste,

  • efficiently remove toxins from our air and water,

  • and provide us with a potentially unlimited supply

  • of renewable clean energy.

Have you ever seen static electricity cause a spark of light?

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B2 TED-Ed plasma magnetic gas charged cube

【TED-Ed】Solid, liquid, gas and … plasma? - Michael Murillo

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    周興文 posted on 2015/08/04
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