Conduction in Gases
. Gases normally contain few free electrons and are generally insulators. When a strong potential difference is applied between two points inside a container filled with a gas, the few free electrons are accelerated by the potential difference and collide with the atoms of the gas, knocking free more electrons. The gas atoms become positively charged ions and the gas is said to be ionized. The electrons move toward the high-potential (more positive) point, while the ions move toward the low-potential (more negative) point. An electric current in a gas is composed of these opposite flows of charges.