“The branch of physics which deals with the study of the properties of plasma is known as plasma physics.”
A highly ionised gas is regarded as a fourth state of matter called the plasma state.It is regarded as fourth state of matter since it is not solid,liquid or gas in usual sense.
How to create plasma?
The kinetic energy of gas molecules goes on increasing if a gas is heated continuously.This causes the gas molecules to move faster and faster.The collision between atoms and molecules of the gas become so strong that they tear off the atoms.Atoms lose their electrons and become positive ions.This ionic state of matter is called plasma.Plasma is formed in gas discharge tubes when electric current passes through these tubes.
Properties of plasma state of matter:
An important property of plasma is that it can sustain oscillation.It can be explain in the following manner.Since the plasma has equal number of electrons and positive ions,it behave almost like a neutral gas.It means that it produces no resultant electric field.However,if at any instant,one region of the plasma has excess and other deficiency of charge,an electric field will exist there.The positive ions will rush along the direction of field and electrons opposite that direction to reduce the field is zero.But positive ions and electrons moving in opposite direction will over shoot due to the previous one.Now the positive ions will rush back and whole process will repeated again and again.In this way,the plasma can sustain oscillation,once they are excited.
The most important property of plasma is that it can develop a very high temperature.The temperature inside a heavy spark may rise the several million of degrees centigrade.Such a high temperature can start the process of fusion and so it provides as one method of producing atomic energy on a large scale.Nature is using this method for the production of atomic energy in the stars,which are regarded as big plasma.
A high temperature plasma can be produced with in intense spark by discharging a large number of capacitors connected in parallel.But it is very difficult to control a plasma because it cannot be kept bound in a vessel since no solid can stand such a high temperature.Many attempts have been made to control the plasma by using a strong magnetic field.Since charged particle can be kept moving around a magnetic field .