Plasma Everywhere

How does plasma form in Tesla Coils?
- John Yu (age 17)
Lancaster, PA, Lancaster

You probably already know that the difference between plasma and ordinary air is that plasma contains many charged particles- ions and electrons- and not just electrically neutral molecules. Very large electric fields can simply rip apart molecules, pulling the negatively charged electrons one way and the positively charged nuclei the other way. However, if I understand right, Tesla coils do not need such large fields. So long as there are a few charged particles in the air to begin with, the electric fields from the Tesla coils will accelerate them to high speeds. When they bump into neutral molecules, the impact can ionize the neutral molecule. A chain reaction of these events gives a plasma.
Fluorescent lights are another familiar device that uses a plasma. You’ve probably noticed how they often have trouble getting started. That’s because they need enough ions to get the ionization process going, requiring special starter circuits.

Adam and Mike W

(published on 10/22/2007)