Hence electric discharge takeplaced at high potential and low pressure. It is because when the gas is at very low pressure positive charged ions are not available to eject out the electron from the cathode hence the discharge current stops.No, vacuum cannot conduct electricity.
Why the electrical discharge through the gases could be observed only at very low pressures and at very high voltages?
1) why the electrical discharge through gases could be observed only at low pressures and very high voltage ? Ans: Gases are poor conductors hence, High voltage is applied to make the gases conducts electricity.
Why low pressure is used in discharge tube?
You need the low pressure in the tube so that the passage of the beam of electrons is not impeded very much by collision with air molecules. You need a reasonably high accelerating voltage to give the electrons enough kinetic energy to make the fluorescent screen glow when the electrons hit the screen.
Why does low pressure gas glow at a lower voltage than high pressure gas?
Because charge carriers are moving in space. They are rubbing against each other, part of the energy is dissipated and goes into heat and other is emitted and you see your glow.
What was the reason for passing high voltage and maintaining low pressure conditions in the above experiment?
High pressure means more number of gas particles. More number of gas particles leads to increased number of collisions with ejected electrons(contained in the cathode rays). This decreases the energy of the electrons and hampers the experimental observations. So, a low pressure gas is used in a cathode ray experiment.
Why does gases become conduction at low pressure?
At low pressure molecules of gas are far from each other due to which gas molecules have enough mean free path to accelerate. … As the ionization of molecules will occur there will be free electrons as we know that free electrons conduct electricity. And this is why gases conduct electricity at low pressure.
Why does not discharge takes place at low pressure?
Due to this reason a gas (air) a conductor of electricity at low pressure. … It is because when the gas is at very low pressure positive charged ions are not available to eject out the electron from the cathode hence the discharge current stops.No, vacuum cannot conduct electricity.
What is discharge tube explain with diagram?
Discharge tube is also called “CROOCK TUBE”. It is made of a glass tube which consists of two metallic plates. … In discharge tube experiment, at low pressure and at very high voltage, an electric current is passed. Due to passage of electric current, a stream of rays is passed in the tube originating from cathode.
Why the tube is evacuated?
Thermionic Emission and Radioactivity
i) The cathode ray tube is evacuated to a low pressure so that the electrons may move without being obstructed by air molecules.
What happens in the discharge tube if a high voltage is applied at gas pressure of one atmosphere?
When high voltage is applied to the tube, the electric field accelerates the small number of electrically charged ions and free electrons always present in the gas, created by natural processes like photoionization and radioactivity.
Why cathode rays are produced at low pressure?
At low pressure (10−2 atm) and higher voltage (10000 V) gases are partially ionised in the discharge tube. Positive ions of gases strike on the cathode. Due to the thermal effect, a beam of electrons releases from the surface of the cathode. This is called a cathode ray.