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Plasma (physics)

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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.
Gas-filled tubes often contain plasma. This one shows neon. The color of the tube gives a hint to the gas inside.

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 loses heat, the ions will re-form into a gas.

Over 99% of the matter in the visible 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 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 the 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.

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