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Author Topic: Why Non-Conductor Materials Get Charged ?  (Read 2838 times)

Offline blue_cristal

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Why Non-Conductor Materials Get Charged ?
« on: 04/11/2012 00:40:17 »
If non-conductor materials like a rubber or glass rod have no free electrons then why they get charged with friction ? Is it due induction ( atomic polarization ) or something else ?


 

Offline lightarrow

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Re: Why Non-Conductor Materials Get Charged ?
« Reply #1 on: 04/11/2012 18:48:05 »
Not even conductors have "free" electrons. Conductors have electrons, or other charges, who are free to move inside of it (it's not the same thing).
But even non-conductors have charges, e.g. electrons, which can be added or taken away from the material: it consists of atoms, with positive nuclei and negative electrons around, anyway.
 

Offline blue_cristal

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Re: Why Non-Conductor Materials Get Charged ?
« Reply #2 on: 05/11/2012 00:12:04 »
lightarrow, but that is what I meant when I said "free electrons".

But thank you for the rest of the explanation. In other words, if I understood correctly, some atoms of, both, non-conductor and conductor materials can gain or lose electrons ( hence becoming electrically charged ) but besides electrons being exchanged through friction, in conductors they can move through an entire object. Is that correct ?
 

Offline evan_au

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Re: Why Non-Conductor Materials Get Charged ?
« Reply #3 on: 05/11/2012 02:04:45 »
With a charged conductor, if you add (or subtract) some electrons, the electric charge:
  • quickly redistributes itself over the surface of the whole object (which reduces the local charge)
  • rapidly discharges itself to ground, or through the person holding it, or into the air (from any sharp edges or points)
With an insulating material, the charge stays localised where it was created, and doesn't discharge nearly as fast. This makes it easier to demonstrate the effects of static electricity.

Some of these principles are visible in a Van de Graaf generator, on display at many science labs and museums.
  • Friction on an insulating belt creates a charge, and carries it up to a ball
  • The charge distributes itself to the outside of the ball
  • The ball is insulated from ground by a transparent column
  • The ball has no sharp edges to produce discharges to air
  • This mechanism would not work if you made the belt out of a conductive material.
  • http://en.wikipedia.org/wiki/Van_de_Graaff_generator
 

Offline blue_cristal

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Re: Why Non-Conductor Materials Get Charged ?
« Reply #4 on: 08/11/2012 21:09:27 »
evan_au, thank you for these precious details about distribution of charges. Very enlightening.
 

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Re: Why Non-Conductor Materials Get Charged ?
« Reply #4 on: 08/11/2012 21:09:27 »

 

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