What is the phenomenon

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
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?
 

#12

Joined Nov 30, 2010
18,210
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.
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
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.







 

Glenn Holland

Joined Dec 26, 2014
705
Great video.
Graphite is a semi metal and it is an electrical conductor. It is non-inductive, and has a negative temperature coefficient.
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.
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
That is enough time for you to have bought an ohm meter. Measure it yourself.
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.

I have done that at 5V 40Amps supply.
And It is burning as show in video now it taken some seconds to blow out.
 

shortbus

Joined Sep 30, 2009
7,760
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.
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.
 

WBahn

Joined Mar 31, 2012
25,910
Pencil lead is graphite mixed with a ceramic powder...the harder the lead (lower number) the more ceramic.
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.
 

shortbus

Joined Sep 30, 2009
7,760
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.
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.
 
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