#6a.   The Fluorescent Lamp:
      A plasma you can use

http://www.phy6.org/Education/wfluor.html

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---   A plasma is a gas containing free electrons and positive ions. It conducts electricity.

---   Sun, magnetosphere, ionosphere and solar wind are all plasmas. So is the gas inside a fluorescent tube.

---   A few free ions and electrons are always around--due to radioactive traces, etc. The voltage on the tube accelerates them, they collide and knock off more electrons in the gas. The plasma quickly gets much denser.

---   The ballast coil stops the plasma from getting too dense, and the current too big.

---   Electrons and ions recombine all the time, and produce light. The fluorescent paint on the inside converts useless ultra-violet to visible light.