Cathode ray tube- thermionic emission

In summary, the cathode ray tube has an electron gun that emits electrons which strike the fluorescent screen. To prevent loss of electrons, there is a circuit connecting the screen back to the electron gun, either through a power supply or through grounding.
  • #1
Nemika
28
0
I have just learned about the cathode ray tube in the class room. There is a part called electron gun in it which emits electrons and these electrons finally strike the fluorescent screen.(I hope its correct till here.) But I want to ask that won't there be a loss of electrons in this process since the fluorescent screen is not connected in a circuit to pass these electrons to the initial atoms from which they where lost.
Thanks in advance for any reply.
 
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  • #2
There is a circuit connecting the fluorescent screen back to the electron gun. There is a conductive layer incorporated into the phosphor screen to conduct the electrons away. Without this, the phosphor screen would charge up to a large negative potential until it repels the incoming electrons and the CRT ceases to function. The conductive layer conducts the electrons back to ground so there is a complete circuit between the electron gun and the phosphor screen.
 
  • #3
phyzguy said:
There is a circuit connecting the fluorescent screen back to the electron gun.
So does this circuit takes these electrons back to the electron gun or are they earthed(I found the second one on a website).
 
  • #4
Nemika said:
So does this circuit takes these electrons back to the electron gun or are they earthed(I found the second one on a website).

Typically both the electron gun and the phosphor screen are connected to a ground (earth) potential. This gives a path for the electrons to flow from the phosphor screen back to the electron gun. They can't be directly connected together because they are at different potentials. It doesn't really matter whether the electrons flow from the phosphor screen, through a power supply and back to the electron gun, or whether electrons flow from the phosphor screen to ground and other electrons flow from ground to the electron gun. The net result is the same.
 
  • #5
Thanx for clearing my doubt.
 

1. What is a cathode ray tube?

A cathode ray tube, also known as a CRT, is a vacuum tube that uses thermionic emission to produce a focused beam of electrons. It is commonly used in old television sets and computer monitors.

2. How does thermionic emission work?

Thermionic emission is the process of releasing electrons from a heated filament into a vacuum. This creates a cloud of electrons that can be manipulated and focused by electric and magnetic fields to create an image on the screen of a CRT.

3. What are some applications of cathode ray tubes?

Cathode ray tubes were commonly used in old television sets and computer monitors. They are also used in oscilloscopes, electron microscopes, and other electronic devices that require a focused beam of electrons.

4. What are the advantages of using cathode ray tubes?

Cathode ray tubes have a fast response time and can produce high-quality images with good color accuracy. They also have a relatively long lifespan and are relatively inexpensive to produce.

5. Are there any disadvantages to using cathode ray tubes?

One disadvantage of cathode ray tubes is their size and weight, making them less suitable for portable devices. They also consume a lot of energy and are not as energy-efficient as newer display technologies such as LCD and LED screens.

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