I heard that neon signs contain plasma, why aren't they hot?
is it because the electrons and ions do not hit the lamp's wall?
Is it because it is non thermal plasma and electrons and ions are not in thermal equilibrium?
If that is the case do the electrons and ions and neutral atoms (all of them) hit the lamps wall?
[Physics] Why doesn’t a neon sign seem that hot
electricityeveryday-lifeplasma-physicsthermodynamics
Best Answer
There is a difference between temperature and energy.
Plasma is, as you said, very hot - but there isn't very much of it. The density of plasma in the tube is very low. So when it does hit the walls of the tube it transfers very little energy. So the mass of the glass tube increases in temperature only very slightly.
It's like a firework sparkler, the sparks are at 2000degC but they are very small, have very little mass and contain very little energy - so when one lands on you it transfer much less energy than a hot cup of coffee at 80deg C.