Plasma (physics)

A plasma lamp, showing some of the more complex things a plasma can do. The colors come from the gas in the lamp. Each type of gas makes a different color.

Plasma is a form (also called state) of matter. The three other common states of matter are solids, liquids and gases, so plasma is sometimes called the fourth state of matter. Plasma is created by adding energy to a gas so its atoms and molecules separate (called ionization) into negatively charged electrons, and positively charged ions. Unlike the other states of matter, the charged particles in a plasma will react strongly to electric and magnetic fields (i.e. electromagnetic fields). If a plasma gets cold, the ions will re-form into a gas.

Over 99% of the matter in the universe is believed to be plasma. When the atoms in a gas are broken up, the pieces are called electrons and ions. Because these pieces have an electric charge, they are pulled together or pushed apart by electric fields and magnetic fields. This makes a plasma act different from a gas. For example, magnetic fields can be used to hold a plasma, but not to hold a gas. Plasma is a better conductor of electricity than copper.

Plasma is usually very, very hot, because it takes very high temperatures to break the bonds between electrons and the nuclei of the atoms. Sometimes plasmas can have very high pressure, like in stars. Stars (including our own Sun) are mostly made of plasma. Plasmas can also have very low pressure, like in outer space.

On earth lightning and aurora make plasma. Artificial (man-made) uses of plasma include fluorescent lightbulbs, neon signs, and plasma displays used for television or computer screens. Scientists are experimenting with plasma to make a new kind of nuclear power, called fusion, which would be much better and safer than ordinary nuclear power, and would produce much less radioactive waste.

Related pages

• Gas
• Liquid
• Solid

Other websites

• Plasmas: the Fourth State of Matter
• Plasma Science and Technology
• Plasma on the Internet comprehensive list of plasma related links.
• Introduction to Plasma Physics: Graduate course given by Richard Fitzpatrick | M.I.T. Introduction by I.H.Hutchinson
• NRL Plasma Formulary online (or an html version)
• Plasma Coalition page
• Plasma Material Interaction
• How to make a glowing ball of plasma in your microwave with a grape | More (Video)
• How to make plasma in your microwave with only one match (video)

• U.S. Dept of Agriculture research project "Decontamination of Fresh Produce with Cold Plasma"
• (French) CNRS LAEPT "Electric Arc Thermal Plasmas
• "Phases of Matter". NASA. http://www.grc.nasa.gov/WWW/K-12/airplane/state.html. Retrieved 2011-05-04.