Can an Insulator Acquire Same Charge as Charged Body?

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Discussion Overview

The discussion centers around whether an insulator can acquire the same charge as a charged body through various means such as induction or contact. The scope includes theoretical considerations and practical examples related to electrostatics and charge transfer mechanisms.

Discussion Character

  • Debate/contested, Technical explanation

Main Points Raised

  • Some participants assert that when a charged body is brought near an insulator, the side facing it acquires a charge of opposite sign due to induction.
  • One participant claims that an insulator can acquire the same charge as a charged body, citing the operation of a van deGraaff generator as an example.
  • Another participant argues that charge cannot be induced on insulators and that in high electric fields, charge can be deposited in insulators rather than induced.
  • A later reply elaborates on the van deGraaff generator, suggesting that charge is wiped onto the dielectric belt and then transferred to the metal sphere, where it can accumulate.

Areas of Agreement / Disagreement

Participants express differing views on the ability of insulators to acquire charge, with some supporting the idea of charge acquisition through specific mechanisms while others contest the possibility of induction on insulators. The discussion remains unresolved.

Contextual Notes

Participants reference specific mechanisms like field-emission and charge deposition, indicating that the discussion may depend on the definitions of charge induction and the conditions under which these processes occur.

akhil123
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When a charged body is brought near an insulator, the side facing it acquires a charge of opposite sign because of induction. Is it possible for an insulator to acquire same charge as charged body? (by induction, touching or any other means)
 
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akhil123 said:
When a charged body is brought near an insulator, the side facing it acquires a charge of opposite sign because of induction. Is it possible for an insulator to acquire same charge as charged body? (by induction, touching or any other means)

Yes. The belt on a van deGraaff generator picks up charge in this way.
 
An insulator in an electric field gets charged positively by field-emission of electrons in very high electric fields, or negatively by electrons collected from other field-emitting sources. Charge cannot be induced (Faraday induction) on insulators. In very high voltage situations, charge can get deposited in (as opposed to on) insulators.

Bob S
 
Bob S said:
An insulator in an electric field gets charged positively by field-emission of electrons in very high electric fields, or negatively by electrons collected from other field-emitting sources. Charge cannot be induced (Faraday induction) on insulators. In very high voltage situations, charge can get deposited in (as opposed to on) insulators.

Bob S

I was referring to the "other means" part of the question. In the Wikipedia description of a van deGraaff generator, it looks to me like the combs "wipe" charge onto (or into) the conducting, dielectric belt. Once conveyed to the large metal sphere at the top of the loop, the charges are wiped off of (or out of) the belt by the upper comb, and migrate to the sphere's outer surface where they can build up considerably before spontaneously draining away into the ambient air.
 
Thanks a lot
 
akhil123 said:
Thanks a lot

You're welcome. I know the "scraping" idea is a lame one, but it was how one of these contraptions was explained to me in a high school physics class.
 

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