Why losing charges under light?

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Discussion Overview

The discussion revolves around the phenomenon of static electricity loss in materials exposed to light, particularly in the context of xerographic copiers. Participants explore the processes involved in charge retention and loss, including the role of light and the photoelectric effect, as well as the nature of the charges involved.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the type of charge applied to the material and the process by which it loses charge when exposed to light.
  • Another participant suggests the photoelectric effect as a possible explanation for the loss of charge under light.
  • There is mention of the smell of ozone near copy machines, with a participant asking whether the material is charged positively or negatively before the photoelectric effect occurs.
  • Some participants assert that the material is negatively charged and describe how the charge changes when exposed to light, leading to toner attraction.
  • Discussion includes details about older versus newer machines and their mechanisms for charge application and retention.

Areas of Agreement / Disagreement

Participants express differing views on the specifics of the charge type and the processes involved, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

There are unresolved questions regarding the exact nature of the charge applied and the specific mechanisms at play in different xerographic machines, as well as the dependence on machine design and technology.

oem7110
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Does anyone have any suggestions on what charge of static electricity is being applied into the material?
When this material is exposed to light the areas exposed lose the charge, Does anyone know what kind of process it is for losing the charge under light?
Thanks in advance for any suggestions

"For xerographic copier, a special type of material is used, which is non-conducting in darkness but conductive when exposed to light. While in the dark the materials is charged with static electricity. When it is exposed to light the areas exposed lose the charge, while most not exposed retain the charge. After exposure to light the plate is sprayed with a fine powder of oppositely charged dry ink (toner), which adheres to the areas of the plate, which retained a charge by electrostatic attraction. Finally, a sheet of paper, which is also charged is placed on the plate, and the toner is transferred to the paper. The paper is then heated briefly to make the toner adhere permanently. The excess toner is scraped off the plate, and the entire plate is exposed to light to remove any remaining charge."
 
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Does anyone know what kind of process it is for losing the charge under light?
Photo-electric effect.

The exact charge applied depends on the xerox machine.
 
Simon Bridge said:
Photo-electric effect.

The exact charge applied depends on the xerox machine.

Usually, we can smell ozone gas near the copy machine,
Do you have any suggestions whether the materials is charged with negative or positive static electricity before photo-electric effect?
Thanks you very much for any suggestions
 
oem7110 said:
Usually, we can smell ozone gas near the copy machine,
Do you have any suggestions whether the materials is charged with negative or positive static electricity before photo-electric effect?
Thanks you very much for any suggestions

It is negative charge. The ozone smell happens to be noticed at older machines. Newer ones have a charge roller which is in direct contact with the image drum. Lower voltage too. The laser or the LEDs is lit on the image drum. The charge changes and the negative charged toner will "jump" towards these lit areas.

Vidar
 
Low-Q said:
It is negative charge. The ozone smell happens to be noticed at older machines. Newer ones have a charge roller which is in direct contact with the image drum. Lower voltage too. The laser or the LEDs is lit on the image drum. The charge changes and the negative charged toner will "jump" towards these lit areas.

Vidar

Thanks everyone very much for your suggestions
 

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