why does the presssure have to be very low in a cathode ray tube?

Question

i was told that the electrons wont flow if the pressure is high; is this true? if so, why?

Answer 1

Imagine a car is passing a road.
If the road has 'high pressure' (i.e there are many other cars, high wind, etc) the car cannot go through the road so easily. On the other hand if the road is empty or has low pressure, the car can pass the road withouth any hassle.
Now think as it's like this: the car is an electron, and the road is the cathode ray tube.

Answer 2

The principle of operation of a CRT (Cathode Ray Tube) is that electrons are emitted from a filament and are accelerated towards the phosphor screen by a series of grids. If there is a high pressure in the CRT, the electrons will "bump" into the atoms of the gas and will either be deflected or captured to form ions. In either case, the electrons will not reach their target and so, an image will not be formed on the screen. Inert gases are used in some vacuum tubes because they will not ionize, so they have a lesser effect on the electrons.

Electrostatic air ionizers are an example of where electrons are intentionally used to bombard atoms, so that ions are formed. Of course, these machines rely on air pressure to be effective.

Answer 3

It's not as much a question of pressure as it is of density. Pressure and density are directly proportional at a constant temperature, so this point can get confused.

If the tube is not filled with vacuum (i.e., near 0 density), the electrons could deflect off of other particles in the space. That deflection would prevent them from delivering their energy to the screen (where it is converted into light).

So it's not so much that electrons won't flow in "high pressure." High pressure (at room temperature) implies a high particle density, which would give the electrons lots of objects to hit on their way to the screen.

Answer 4

Pressure is an external force acting on the body. It will oppose the flow of electrons from the cahode . For electrons to flow u wud have to apply more voltage across the CRT.

Answer 5

Cat tubes are like light bulbs, partial vacuums inside, or, noble gases.

A television tube is like a big light bulb, but instead of one filament, it has an array. You can think of a Cat tube like a speaker in your stereo too .... the signal at the input side is amplified across the vacuum of the tube and then you see the signal as various ions emit light proportionate to the signal fluctuations ... ie , you see the picture which was transmitted.

Answer 6

The one just above this one is the correct answer. The rest are just sorta making it up as they go...