Cathode Ray Tube: Positive End & Electrons Explained

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Discussion Overview

The discussion revolves around the terminology and concepts related to cathodes and anodes in cathode ray tubes, particularly focusing on the nature of electrons emitted from the cathode and the implications of their movement in electric fields. It touches on theoretical aspects, definitions, and the underlying physics of thermionic emission.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question why the cathode, where negatively charged electrons are emitted, is associated with the term "cat," suggesting that "cat" implies positivity in chemistry.
  • Others assert that the cathode is considered positive because it emits or "loses electrons," leading to a positive charge.
  • A participant introduces the concept of thermionic emission, explaining it as the process by which charged particles are emitted from a heated surface, such as the cathode in a cathode ray tube.
  • One participant challenges the notion that the cathode's designation as positive is meaningful, arguing that electron movement is dictated by potential differences rather than the charge of the electrodes.
  • There are repeated references to thermionic emission, indicating its relevance to the discussion but also prompting questions about its definition and implications.

Areas of Agreement / Disagreement

Participants express differing views on the terminology and implications of cathodes and anodes, with no consensus reached on the significance of the terms or the underlying physics of electron movement.

Contextual Notes

Some statements rely on specific definitions of charge and potential, which may not be universally accepted. The discussion also reflects varying levels of understanding regarding thermionic emission and its role in cathode ray tubes.

pivoxa15
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Why is the end of the hot filament where negatively charged electrons are being fired called the cathode end. 'cat' in chemistry means positive, I assume the same goes in physics as well?
 
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cathode is called cat or positive because it is emitting or "losing electrons" thus making it positive or cat
 
remember thermo ionic emission
 
hustleberry said:
remember thermo ionic emission

What is thermo ionic emission?
 
Thermionic emission is the emission of charged particles from a charged surface (usually metal), which is caused by the vibration energy of the particles overcoming the electrical potential holding them to the surface. An example of this would be your cathode ray tube where a charged filament is heated (by passing a large current through it), the electrons on the surface of the filament (remember charge always resides on the surface of a conductor) gain enough thermal energy to 'break free'.

For more detail google: Thermionic Emission
 
hustleberry said:
cathode is called cat or positive because it is emitting or "losing electrons" thus making it positive or cat

So that is the main reason. The receiving end is receiving the electrons hence will be made more negative so that end is called the anode.
 
pivoxa15 said:
So that is the main reason. The receiving end is receiving the electrons hence will be made more negative so that end is called the anode.

That doesn't make any sense either. An electron will move from a low electrostatic potential to a high potential. It has nothing to do with something being negative or positive. I could have the electrons coming out of a conductor at -10 V and it will still be "attracted" to a conductor at - 5 V, because that latter conductor is at a higher potential. The difference in the potential will create a potential gradient, thus, electric field.

At some point, one should stop getting bogged down with the "name" given to something. If you understand what is going on, you can call it anything you like.

Zz.
 

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