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?

 

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.

 

OK, That mean the pencil lead is carbon resistor.
then what is the resistance of it?

 

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.

 

Give it enough current and it will burn up...just like any other resistor.

I have done that at 5V 40Amps supply.
the small front knob of pencil it does not happen.

 

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

 

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.

 

OK, That mean the pencil lead is carbon resistor.
then what is the resistance of it?

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.

 

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.

 

I suspect most fuses glow brightly before burning out.

 

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.

 

I suspect most fuses glow brightly before burning out.

The glass fuses do, but those pesky cartridge fuses neither say nor show any sign when retiring from the business.

 

He also should by now be able to Google his questions.

Profound ignorance goes with the job here. Failure to make any effort to help your self eventually becomes self defeating.

 

OK, That mean the pencil lead is carbon resistor.
then what is the resistance of it?

Pencil lead is graphite mixed with a ceramic powder...the harder the lead (lower number) the more ceramic.

 

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.

 

how I am confused.

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

 

Profound ignorance goes with the job here. Failure to make any effort to help your self eventually becomes self defeating

how to overcome this?

 

how to overcome this?

Set your sights on something a bit less challenging?

 

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.

 

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.

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