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enter image description here

I understand that/ obviously, opposite charges will attract?

However, I am still slightly confused about what happens if an insulator becomes charged. How come an insulator, which is charged, will not attract with a conductor which is charged?

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You see the main concept to understand here is that insulators are usually charged by friction while conductors are usually not. This has to do with the ease of electron transfer.

Remember that once an insulator gains or loses electrons it it difficult to undo that charge (e.g. Lose the electrons it has gained as it is difficult for movement of charge inside it). In an insulator if you rub it( like the plastic lunch wrap) there is frictional force on its surface and so once some electrons are transferred and it stays relatively charged even with further rubbing.( e.g. it can gain 10 electrons and maybe lose just 2 as once electrons are gained they are harder to lose)

However, with a conductor the ease of electron transfer is much higher. So as friction occurs with rubbing or rubbing with another charged insulator etc. electrons are gained but they are also lost roughly by the same amount. ( e.g. 50 gained and 50 lost ). Thus a conductor is harder to charge by rubbing etc. thus it is usually not charged.

Also the question you have asked is not related to the one in the picture as indeed a charged insulator will attract a charged conductor but understand that crumpling an aluminum foil does not make it charged as I have explained above why.

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    $\begingroup$ Thanks so much for your help. Are the electrons (extra ones gained) usually earthed/grounded? $\endgroup$ – Christopher Uren Sep 16 '17 at 6:30
  • $\begingroup$ Yes in a sense you can say that but it is really the loss=gain. $\endgroup$ – Tausif Hossain Sep 16 '17 at 6:37

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