Types of energy in a gas discharge tube

[Bhope69199]

I am reading about gas discharge tubes and can't work out the types of energy and energy conversion that occurs in a gas discharge tube.

Initially before the tube is switched on you have an inert gas with kinetic energy.

As soon as the tube is switched on there is an an electric field between two electrodes which ionises the gas. The energy is provided by the power source as say chemical energy. This chemical energy is being converted into electrostatic potential energy within the electrodes. This electrostatic potential energy is transferred through the electric field to the gas ions.

This electrostatic potential energy is then converted to kinetic energy once the ions are accelerated towards the electrodes.

Once they hit the electrodes this kinetic energy is transferred to the electrodes and back into the power source or lost through the collision with the electrode.

Do the electrodes lose electrostatic potential energy once the gas is ionised (as it is being transferred to the gas ions?)? And is this being replaced by the movement of electrons to the electrodes by the power source? (Chemical energy into electrostatic potential energy in the case of a battery?)

Is this process of energy transfer correct in this case and are there any other energy transfers that I am missing?

Thanks.

 

[Charles Link]

An important characteristic of gas discharges is in many cases, besides atoms being ionized and thereby creating free electrons, there are also atoms with excited electronic states of their atoms. Both ions and free electrons, and excited electronic states can result in spectral lines as the atom transitions to a lower energy state. In addition , mostly from the plasma (ionized gas) itself, there can be a blackbody type (continuous spectrum roughly following the Planck blackbody function) spectral output from these lamps in addition to atomic spectral lines.

 

[Drakkith]

Initially before the tube is switched on you have an inert gas with kinetic energy.

That's right.

As soon as the tube is switched on there is an an electric field between two electrodes which ionises the gas. The energy is provided by the power source as say chemical energy.

The power source provides electrical energy in the form of a current and voltage.

This chemical energy is being converted into electrostatic potential energy within the electrodes. This electrostatic potential energy is transferred through the electric field to the gas ions.

This electrostatic potential energy is then converted to kinetic energy once the ions are accelerated towards the electrodes.

Once they hit the electrodes this kinetic energy is transferred to the electrodes and back into the power source or lost through the collision with the electrode.

Several things are happening in the gas. Electrons are being ripped out of their orbitals by the electric field and by collisions between high-energy electrons or atoms. These free electrons then have both kinetic energy and several forms of potential energy (since they can be captured by another ionized atom, releasing energy, and they are also in an electric field). Overall, the influx of energy from the electrodes heats the gas in the tube, increasing its internal energy (kinetic + potential). All this moving about of charges and transitions between energy states releases energy in the form of light. Heat is also lost, transferred from the gas to the lamp glass and then to the environment. Shortly after being switched on, the lamp reaches equilibrium where the energy being released from the lamp in the form of light and heat equals the energy input to the lamp.

Do the electrodes lose electrostatic potential energy once the gas is ionised (as it is being transferred to the gas ions?)? And is this being replaced by the movement of electrons to the electrodes by the power source? (Chemical energy into electrostatic potential energy in the case of a battery?)

While the power source is turn on, the net effect is that the electrodes maintain a steady-state situation where they aren't losing or gaining any net energy. You can try to talk about what happens to individual electrons, but even that's a bit difficult as there are many different things happening at the electrode-gas boundary. Furthermore, energy isn't transferred to the electrodes solely through electrons. The electromagnetic field is how most of the energy is transferred from the power source to the electrodes and then to the gas.

That's my understanding at least.