Drain current in a CRO

Discussion in 'General Electronics Chat' started by dheena, Jul 27, 2004.

  1. dheena

    Thread Starter New Member

    Jul 15, 2004
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    Can anybody explain how the electrons emitted by the electron gun drained in a continuous operation of a CRO(Cathode Ray Oscilloscope)? Will draining not affect the pattern formation?
     
  2. haditya

    Senior Member

    Jan 19, 2004
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    what do mean by drained?? do you want to know where the electrons go after they hit the screen?? or what??
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi

    There's a conductive layer behind the phosphors, that used to be called aquadag (or something like that). It's not terribly conductive, but does provide a path to the external return lead. It doesn't affect the display on the screen, because the transfer of momentum from the accelerated electrons excites the phosphors, not their charge. The presence of stray electrons draining off may deflect incoming electrons slightly, but can no longer cause emission by the phosphors.
     
  4. dheena

    Thread Starter New Member

    Jul 15, 2004
    4
    0
    Thanks a lot beenthere.....i guess this(the charges on the conductive layer) is the reason why hairs on the screen get straitened when we leave our hands close to the screen??
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    yes, there's a pretty good static charge on the faceplate. Some dust mops are made to pick up the charge and thus attrasct dust.
     
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