Electric current through Gases

Understanding Ionization

For a gas to conduct electricity, its molecules or atoms must be ionized. Ionization is the process of gaining or losing electrons, which creates positively and negatively charged particles called ions. When a high voltage is applied across a gas, it provides enough energy to free electrons from atoms, resulting in ionization.

These free electrons, in turn, collide with other gas atoms and cause further ionization, creating a chain reaction known as an ionization avalanche.

Types of Electrical Conduction in Gases

There are two primary types of electrical conduction in gases:

• Non-self-sustained Conduction: Requires an external source like UV rays or radioactive materials to provide ionization. Once the source is removed, conduction stops.
• Self-sustained Conduction: Continues without an external ionizing source, typically achieved when the applied voltage is sufficiently high to maintain ionization through collisions.

Gas Discharge and Glow

When a gas becomes ionized, it may emit light, a phenomenon observed in devices like neon signs and fluorescent lamps. This emission is due to the excitation and subsequent de-excitation of gas atoms, which release photons in the visible range.

The color of the glow depends on the type of gas used. For example, neon emits a reddish-orange glow, while argon emits a bluish-purple light.

Applications of Electric Current Through Gases

• Neon and fluorescent lighting
• Plasma televisions and displays
• Gas-filled rectifiers and tubes
• Lightning and other natural plasma phenomena
• Particle detectors in nuclear physics

Electric current through gases is a fascinating concept that bridges the gap between classical electricity and plasma physics. By understanding how gases conduct electricity, scientists and engineers have been able to create a wide range of technologies that have transformed modern life.