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I've read that Stephen Gray in his experiments on electricity, he has found that static electricity can be conducted -transferred- through an insulator thread made of silk. So, how could that happen although it's ana insulator ?

Regards.

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    $\begingroup$ Hi Joe, welcome to Physics SE! Can you give us some indication of where you read this, including pointing to the specific bit where he supposedly finds that the silk thread conducts electricity? As it stands, it's difficult to tell if this is a misinterpretation on your part, or a true artifact of the (small but finite) conductivity of silk which he observed in the experiment. $\endgroup$ – tok3rat0r May 13 '15 at 23:21
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    $\begingroup$ He found that silk is a bad conductor of electricity and will allow only a very small current to flow through it. There is no such thing as a perfect insulator. $\endgroup$ – SpiderPig May 13 '15 at 23:42
  • $\begingroup$ Unless the measurements were done in dry nitrogen or vacuum after the fibers had been dried for a considerable amount of time, the results are probably not particularly reliable. $\endgroup$ – CuriousOne May 14 '15 at 2:15
  • $\begingroup$ Stephen Grey published many of his experiments in the "Philosophical Transactions" in 1731. The original text can be found on the website of the royal society. rstl.royalsocietypublishing.org/content/37/417-426/… $\endgroup$ – SpiderPig May 14 '15 at 2:59
  • $\begingroup$ Hey, thanks for your concern. Yes I'm sorry, He only used the silk to support the thread line. BUT he also said that he used a wooden rod, a cork and a pack-thread and they all conducted electricity although they are insulators. This is indication from 'A history of electricity' book :- "Into the cork in the glass tube he inserts a wooden rod four inches long, hav- ing an ivory ball—which he “happened to have by him ” —at its end. The ball attracts brass foil when the tube is rubbed." The book link $\endgroup$ – Joe May 20 '15 at 22:25
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Gray and a friend, Jean Desaguliers, conducted experiments which showed that objects such as cork, as far as eight or nine hundred feet away, could be electrified by connecting them to the glass tube with wires or hempen string. They found material such as silk would not convey electricity.

Source: http://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/lecture_2.html

This contradicts your source - or your reading of it; certainly the usual observation is that silk is a very poor conductor of electricity.

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  • $\begingroup$ Hey,thanks for your concern.Yes I'm sorry, He only used the silk to support the threadline. BUT he also said that he used a wooden rod,cork and a packthread and they all conducted electricity although they are insulators. $\endgroup$ – Joe May 17 '15 at 20:46
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    $\begingroup$ "Into the cork in the glass tube he inserts a wooden rod four inches long, hav- ing an ivory ball—which he “happened to have by him ” —at its end. The ball attracts brass foil when the tube is rubbed." from 'A history of electricity' book. https://archive.org/stream/historyofelectri00benjrich#page/472/mode/2up @tok3rat0r $\endgroup$ – Joe May 17 '15 at 20:53
  • $\begingroup$ A small amount of moisture content is sufficient for something the diameter of a wooden rod to conduct a small amount of charge. The silk, being so much thinner, would appear to be a much better insulator even when the bulk resistivity of both might be similar. Note also the wood was only four inches long. $\endgroup$ – Floris May 17 '15 at 21:23

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