How fast do CRTs shoot electrons?

  • Thread starter Ralphonsicus
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In summary, the conversation discusses the speed at which CRTs (cathode ray tubes) shoot electrons and how it relates to the speed of light. It is mentioned that electrons have mass and therefore cannot reach light speed according to special relativity. The question is then clarified to be about the average speed of CRTs shooting electrons. It is noted that the voltage of a CRT TV cathode is 400 V, which can accelerate electrons to 400 eV of energy, resulting in a speed of 1.18*10^7 m/s or ~4% of the speed of light. The conversation also mentions that in a large tube-TV, the accelerating voltage can be around 25,000 Volts, resulting in a rough
  • #1
Ralphonsicus
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Thanks.
 
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  • #2
It must be less than the speed of light.
 
  • #3
Yes I know that because electrons have mass and therefore (according to special relativity) they cannot reach light speed. But that wasn't the question, the question was HOW FAST do CRTs shoot electrons (on average)?
 
  • #4
Ralphonsicus said:
Yes I know that because electrons have mass and therefore (according to special relativity) they cannot reach light speed. But that wasn't the question, the question was HOW FAST do CRTs shoot electrons (on average)?

With a quick bit of googling I found that the voltage of a CRT TV cathode is 400 V. Therefore an electron accelerated will obtain 400 eV of energy. The speed of an 400 eV electron is 1.18*10^7 m/s or ~4% of the speed of light.
 
  • #5
  • #6
Oops, don't know how I came up with 400 V. Maybe that's for a ye olde oscilloscope or something.
 
  • #7
Haha it's grand, thanks all.
 

1. How are electrons accelerated in CRTs?

Electrons are accelerated in CRTs through the use of an electron gun, which applies a high voltage to a metal plate called the cathode. This causes electrons to be emitted from the cathode and accelerated towards the screen.

2. What determines the speed of the electrons in a CRT?

The speed of the electrons in a CRT is determined by the strength of the electric field created by the electron gun, as well as the voltage applied to the cathode. The higher the voltage and electric field strength, the faster the electrons will be accelerated.

3. Is the speed of electrons in a CRT constant?

No, the speed of electrons in a CRT varies depending on the specific location within the tube. As they travel towards the screen, they may be affected by magnetic fields or other factors that can alter their speed.

4. How fast do electrons typically travel in CRTs?

The speed of electrons in CRTs can vary, but on average they travel at speeds of around 10% of the speed of light, which is approximately 30,000 kilometers per second.

5. Can the speed of electrons in CRTs be controlled?

Yes, the speed of electrons in CRTs can be controlled by adjusting the voltage and electric field strength applied to the cathode. This allows for precise control of the electron beam and the display on the screen.

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