Saturday 9 February 2013

What is Plasma ?

Plasma is a phase of matter distinct from solids, liquids, and gases. It is the most abundant phase of matter in the universe -- both stars and interstellar dust consist of plasma. Although it is its own phase of matter, plasma is often referred to as an ionized gas. This is similar to a normal gas, except that electrons have been stripped from their respective nucleons and float freely within the plasma. Even if only 1% of the atoms have lost their electrons, a gas will display plasma-like behavior.
Plasma is electrically conductive and can be manipulated by magnetic fields. It can be found in a variety of everyday contexts, including plasma displays, fluorescent lamps, neon signs, plasma balls, photolithographic etching machines, flames, lightning, aurora borealis, tesla coils, and more.
Plasmas vary widely. Some parameters used for their classification are the degree of ionization, temperature, density of the magnetic field, and particle density. For example, the gas in a candle flame is only very slightly ionized, whereas the air in the path of a lightning bolt is highly ionized. Some plasmas are very low temperature, like the intergalactic medium, while some are very high temperature, like the center of a star.



Unlike gases, which are composed of neutral atoms, charged plasmas have distinct constituents that behave on their own accord. Free electrons are negatively charged. The nuclei, lacking electrons, are positively charged ions. Most plasmas still contain whole atoms which are electrically neutral as well. Since each of these components can behave differently in response to changes in external and internal conditions, a variety of complex wave-like phenomena can emerge.
Plasma phenomena can be observed safely in your own home with the use of a plasma ball. A plasma ball runs an electric field through a charged gas contained within a glass globe. When a person touches the edge of the globe, the plasma responds by sending out visible filaments to the person's finger, demonstrating the tendency of an electric charge to "ground" itself. Complex, fractal patterns can be seen within the ball.
Because plasma can be contained by magnetic fields, it can be made very hot without diffusing heat into a surrounding medium. Plasmas measuring millions of degrees Kelvin have been produced in tokamak reactors, donut-shaped plasma traps. In the not-too-distant future, we may regularly use superheated plasmas to initiate nuclear fusion reactions that produce large amounts of power.

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