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Cathode ray tube?

  1. Jan 2, 2007 #1
    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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  3. Jan 2, 2007 #2


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  4. Jan 3, 2007 #3
  5. Jan 3, 2007 #4
    cathode is called cat or positive because it is emitting or "losing electrons" thus making it positive or cat
  6. Jan 3, 2007 #5
    remember thermo ionic emission
  7. Jan 3, 2007 #6
    What is thermo ionic emission?
  8. Jan 3, 2007 #7


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    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
  9. Jan 4, 2007 #8
    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.
  10. Jan 4, 2007 #9


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    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.

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