Plasma
Introduction
Plasma is one of the four fundamental states of matter, the others being solid, liquid, and gas. It is often referred to as the "fourth state of matter" because its properties are significantly different from the other states. Unlike these three states of matter, plasma does not exist freely on the Earth's surface under normal conditions and can only be artificially generated from neutral gases.
Characteristics
Plasma is a collection of charged particles containing an equal number of positively charged ions and negatively charged electrons. This results in the overall electrical charge of the plasma being neutral, a characteristic referred to as quasi-neutrality. However, because it is composed of charged particles, plasma is highly responsive to electromagnetic fields, which allows it to be controlled and shaped by these fields. This makes plasma incredibly useful in a variety of applications, from plasma displays in televisions to plasma propulsion in spacecraft.
Formation
Plasma can be formed by heating a gas or subjecting it to a strong electromagnetic field. This process, known as ionization, causes the gas atoms to either gain or lose electrons, thus forming ions. The degree of ionization, which is the proportion of atoms that have become ions, can vary between different plasmas. This means that a plasma can actually contain a mixture of ions, electrons, and neutral particles.
Types of Plasma
There are two main types of plasma: thermal and non-thermal, or "cold" plasmas.
Thermal Plasma
Thermal plasmas are those in which the electrons and heavy particles (ions and neutrals) are in thermal equilibrium. This means they have the same temperature, measured in terms of kinetic energy. In thermal plasmas, the temperatures of the electrons and the heavy particles are equal. This is the type of plasma found in stars, including the sun.
Non-Thermal Plasma
Non-thermal, or "cold", plasmas are those in which the electrons are at a much higher temperature (and therefore have a higher kinetic energy) than the heavy particles. In these plasmas, the electron temperature can be hundreds or thousands of times higher than the heavy particle temperature. Non-thermal plasmas are commonly used in fluorescent lights and plasma displays.
Applications
Plasma has a wide range of applications in various fields, from technology to medicine.
Technology
In technology, plasma is used in a variety of applications, including plasma displays, plasma antennas, and plasma propulsion. Plasma displays are a type of flat panel display that uses small cells containing electrically charged ionized gases. Plasma antennas are radio frequency antennas that use plasma as the conducting medium instead of metal. Plasma propulsion systems use electric power to ionize propellant gas into plasma. The plasma is then accelerated to create thrust.
Medicine
In medicine, plasma technology is used in a variety of applications, including sterilization, wound healing, and cancer treatment. Plasma sterilization is a non-thermal plasma application that is used to sterilize medical and dental equipment. Plasma is also used in the treatment of wounds and ulcers, where it helps to kill bacteria and promote healing. In cancer treatment, cold atmospheric plasma is used to kill cancer cells.