I’ve looked up a few physics pages and I still have difficulty grokking plasma.
I kinda get that the heat messes with the electrons that compose molecules and atoms in such a way that they are not electromagnetically balanced and I guess that ionization can be useful in some way. Electromagnetic fields are created although I haven’t the faintest idea what that implies.
I do have difficulty understanding what the means in terms of its properties in contradistinctions with gas.
A lot of websites that explain the bottom line will list applications but do not really explain what those applications have in common and why using plasma makes more sense than using a gas.
For example, why would we choose to cut and weld using plasma instead of merely a really hot gas? Why use plasma thrusters rather than just a really hot gas thrusters?
In short, a lot of explanations of plasma go from the pure science of “ionization occurs when electrons are substracted or added to the molecule or atom” to displaying very concrete applications of “look-at-this-cool-plasma-tv-and-thruster-and-lamp-and-cutting” but I’m missing the part that belongs in-between.
This is just a qualified guess, but from browsing through the wikipedia articles on plasma cutters and plasma thrusters my impression is that it’s not about using a plasma instead of just a hot gas, for these two technologies, it’s that they’re technologies for heating/accelerating a gas that happen to produce plasma.
The intention with the plasma cutter is to use gas that is 28000 C.
The result is that the gas is the plasma state ,because its inevitable at that temperature.
In the plasma state, there is no such thing as molecules. eg the N2 gas from the atmosphere splits up and becomes singular Nitrogen atoms. Same with the O2… there’s just free O atoms floating around.
So anyway when the plasma cools, these atoms are free to form molecules of whatever is their will…
For example, it might form some O2, or O3 … ozone… there may be some N2, or some Nitrous Oxide… well these gases come out of your automobile engine anyway, in far greater quantity…
There may be some Iron metal or iron oxide …these may stick together into nano-particles. However its a small amount and I guess ordinary solid steel (and every substance… ) leaks nanoparticles ANYWAY.
I think the smell of the plasma cutter is the ozone , O3… this could be damaging to your health in higher concentrations.
A plasma cutter would not work if plasma didn’t exist…
The way this device works (FWIW, I have one) is like so:
A stream of air is formed into vortex in the nozzle. A pilot arc is struck between two electrodes in the nozzle, which ionizes some of the air, making it conductive. The high voltage existing between the nozzle and the workplace causes an arc in the air leaving the nozzle office, resulting in more ionization, creating the plasma. The energy in the electricity is spent heating the air and turning it into plasma, which is then ejected from the nozzle, and impinging on the workplace. The hot, ionized gas melts the workpiece, help by the energetic re-combination of dissociated air molecules.
If plasma didn’t exist, there would be no way to use an arc to heat the air (in fact, arcs wouldn’t exist).
Note that the vortex is critical to the operation of the device, since it keeps the plasma away from the sides of the nozzle, preventing it from being eroded too quickly (they still don’t last very long - an hour or so at best, for my machine).
Plasma is just what happens to gas when it is heated to very high temperatures. It’s like asking “Why do people drink liquid water instead of eating room temperature ice?” The temperature of a gas is determined by the average kinetic energy of the particles within it. When they get to high enough energy, the collisions between them become violent enough to knock electrons away. Now instead of a gas of electrically neutral particles, you have a gas of separately charged particles (atomic nuclei for positive charge and electrons for negative charge).
For some applications of plasma, it’s the high temperature that’s useful, and for other applications it’s the charge separation that’s useful.
As I mentioned, it’s what makes a plasma cutter possible.
The gas needs to be conducting for it to work. Molecular gasses are non-conducting. It’s only once the gas ionizes (electrons stripped from their atoms) that the gas (now plasma) conducts. This allows a lot of current to flow from the plasma cutter to the workpiece.
A plasma is a gas. It’s a fluid which (approximately) obeys the Ideal Gas Law. It also has some other interesting physical qualities, but nothing in the definition of a gas says there can’t be any other properties.
The main interesting thing about plasmas, in practice, is that they’re electrically conductive.
That is going too far. You have begged the question of how an arc is made ?
If there is no arc without plasma, then the electricity will not arc. With no sparking the plasma will not be made. So therefore, plasma cutters do not exist, or there is a false assumption. The arc can exist without plasma… the arc starts but rapidly heats the air near to be plasma. Not that it matters if it is plasma or molecular.
Wrong.
The plasma cutter has a high voltage generator which causes the air to undergo dielectric breakdown. This ionizes some of the air molecules, which makes the gas sufficiently conducting to allow the low voltage, high current main power of the cutter to flow.
If the air had infinite breakdown strength, there would be no plasma cutters.