What I want to discuss here is what happens to the thermal velocity when an ionised gas molecule has been put into an electric field. Due to the charge (e) and potential difference (V), how much velocity has been gained by the ion can be calculated easily. eV = ½mv2 Where e is the charge of the ion, V is the potential difference, m is the mass of the ion and v is the velocity gained due to the potential difference. From the formula above, it can be easily calculated that v = https://www.physicsforums.com/file:///C:/Users/Payel/AppData/Local/Temp/msohtmlclip1/01/clip_image002.gif [Broken] Now, question is, the gas molecule already has its velocity due to the temperature of the gas that is the Root Mean Square velocity of molecules at that temperature. I want to know whether the velocity gained by the potential difference will be added to the velocity or not.