Plasma definition

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What is "plasma"? How is a fluid measured to be either a gas or a plasma?

Mercury boils at 359 Celsius (632 Kelvin). Mercury vapour is poorly conductive, little ionized (incidentally - monoatomic) and generally defined as a gas.

However, tungsten boils at 5930 C (6203 K).

Photosphere of Sun at 5785 K is generally regarded as plasma, and specifically not gas.

Is tungsten vapour at boiling point a gas, or is it a plasma?

Are there any other elements which lack gas phase because they are plasma at boiling?
 

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  • #2
Vanadium 50
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Plasma is ionized gas.
The sun is not made of tungsten.
 
  • #3
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Plasma is ionized gas.
The sun is not made of tungsten.
Indeed - Sun is made of hydrogen.
H atom first ionization energy is 13,6 eV
W atom first ionization energy is 7,98 eV
Does it mean that at a temperature where H is ionized, W certainly is?
 
  • #4
Drakkith
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What is "plasma"? How is a fluid measured to be either a gas or a plasma?
There are several criteria. From wiki:


Plasma is an electrically neutral medium of unbound positive and negative particles (i.e. the overall charge of a plasma is roughly zero). Although these particles are unbound, they are not "free" in the sense of not experiencing forces. Moving charged particles generate an electric current within a magnetic field, and any movement of a charged plasma particle affects and is affected by the fields created by the other charges. In turn this governs collective behaviour with many degrees of variation.[10][23] Three factors define a plasma:[24][25]

  1. The plasma approximation: The plasma approximation applies when the plasma parameter, Λ,[26] representing the number of charge carriers within a sphere (called the Debye sphere whose radius is the Debye screening length) surrounding a given charged particle, is sufficiently high as to shield the electrostatic influence of the particle outside of the sphere.[21][22]
  2. Bulk interactions: The Debye screening length (defined above) is short compared to the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, where boundary effects may take place. When this criterion is satisfied, the plasma is quasineutral.[27]
  3. Plasma frequency: The electron plasma frequency (measuring plasma oscillations of the electrons) is large compared to the electron-neutral collision frequency (measuring frequency of collisions between electrons and neutral particles). When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics.[28]
 

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