What is the phenomenon

Discussion in 'General Science' started by RRITESH KAKKAR, Dec 1, 2015.

  1. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    Hello,
    I was searching you tube and found this experimental video. In this the lead of pencil glow why?
    is led glow when there is supply on it its legs or terminal?
     
  2. #12

    Expert

    Nov 30, 2010
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    A pencil core is almost the same thing as an old carbon resistor. Give it enough current and it will burn up...just like any other resistor.
     
  3. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    OK, That mean the pencil lead is carbon resistor.
    then what is the resistance of it?
     
  4. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    In this video
    Experiments on refraction, reflection and total internal reflection
    at 00:15 sec The Coin Disappear due to total internal reflection, how i am confused.







     
  5. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    I have done that at 5V 40Amps supply.
    the small front knob of pencil it does not happen.
     
  6. Techno Tronix

    Member

    Jan 10, 2015
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    Great video.
    Graphite is a semi metal and it is an electrical conductor. It is non-inductive, and has a negative temperature coefficient.
     
  7. Glenn Holland

    Member

    Dec 26, 2014
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    Graphite is inductive for the same reason that copper or a superconductor is inductive.

    If a substance can conduct at all, it will have inductance.
     
  8. #12

    Expert

    Nov 30, 2010
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    You have been on this site for over 5 years. That is enough time for you to have bought an ohm meter. Measure it yourself.
     
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  9. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    I have taken 1.25cm lead from pencil measuring resistance from Digital multi meter.
    it is showing non uniform Resistance 12 ohm 5 ohm like this.

    And It is burning as show in video now it taken some seconds to blow out.
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    I suspect most fuses glow brightly before burning out.
     
  11. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    He also should by now be able to Google his questions.

    He was recently banned a ETO for being a troll, for asking questions similar to his recent questions here. He had his name changed to koolguy over there.
     
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  12. #12

    Expert

    Nov 30, 2010
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    The glass fuses do, but those pesky cartridge fuses neither say nor show any sign when retiring from the business.:D
     
  13. #12

    Expert

    Nov 30, 2010
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    Profound ignorance goes with the job here. Failure to make any effort to help your self eventually becomes self defeating.
     
  14. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Pencil lead is graphite mixed with a ceramic powder...the harder the lead (lower number) the more ceramic.
     
  15. WBahn

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    Mar 31, 2012
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    There's more to it than this (as far as my understanding goes). In the H series, a higher number means a harder lead while in the B series a higher number means a softer lead. Most writing pencils are H series while drawing pencils are more likely to be B series.
     
  16. WBahn

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    The more interesting question is how are you not confused? (or at least that would be a much shorter list).
     
  17. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    how to overcome this?
     
  18. WBahn

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    Set your sights on something a bit less challenging?
     
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  19. shortbus

    AAC Fanatic!

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    No, KL7AJ has it correct. Although it is a form of clay added to the graphite, which you could I guess call it ceramic but they don't.
     
  20. WBahn

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    Mar 31, 2012
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    So you are saying that a 2H pencil is harder than a 9H pencil. Really?
     
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