Selenium conducts electricity better in the light than in the dark

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Discussion Overview

The discussion centers around the electrical conductivity of selenium in different lighting conditions, specifically why selenium conducts electricity better in light than in darkness, and its application in photocells.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • Some participants propose that selenium's conductivity in light is due to its nature as a direct gap semiconductor with a band gap of about 2eV, which allows electrons to be excited to the conduction band when exposed to light.
  • One participant questions the behavior of selenium when electricity is passed through it in the dark, speculating that most electricity would not be conducted and wondering about the fate of the remainder.
  • Another participant asserts that the behavior in the dark would be similar to that of any insulator, suggesting a need for understanding basic electrical concepts such as Ohm's Law and resistance.

Areas of Agreement / Disagreement

Participants express differing levels of understanding regarding the basic concepts of conductivity and resistance, with no consensus on the implications of passing electricity through selenium in the dark.

Contextual Notes

Some participants indicate a need for foundational knowledge in electrical concepts, which may limit the depth of understanding in the discussion.

Phy6explorer
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I was reading an article about Selenium and I found that Selenium conducts electricity better in the light than in the dark. Why is that so.And is that why they are used in photocells?
 
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Yes, the reason is the same. Selenium is a direct gap semiconductor with a band gap (if you are not familiar with any of these terms, make sure you look them up) of about 2eV, which is right in the middle of the range of visible light. In the dark, the conduction band is essentially unoccupied, but when light is incident on it, electrons get excited to the conduction band, providing the ability to conduct electricity.
 
But what do you think will happen if I pass electricity through selenium in the dark? I guess that most of the electricity will not be conducted but what will happen to the rest?
 
The same thing that happens with any insulator.

There are some very basic concepts you need to learn first. I suggest you start with Ohm's Law and understand the concept of resistance. Then you can try to understand what conductors and insulators are.
 

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