RE: Gap Question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luke" <Bluu-at-cox-dot-net> 

Antonio:
Thank you for continuing to point out where my concept was wrong.  You
helped me push through and finally get it.  I still had trouble letting
go of looking at it as ohmic value until I read a paper I found online,
http://users.tpg-dot-com.au/users/ldbutler/NegativeResistance.htm.  The
explanation was about the same as what members of the list were trying
to get me to see but the one graph of the V I curve of a tunnel diode
helped me see the light.  I took two points where the slope was positive
and and calculated the resistances at the two points and saw that the
resistance went up a little from point one to point two.  I did the same
for an area of the curve where the slope was negative.  The resistance
also went up but it went up by a very much larger percentage which
caused the current to drop substantially. So in BOTH cases the
resistance went up.  So that helped me see that the ohmic value is not
what negative resistance is meaning.

Thanx.

Luke Galyan
Bluu-at-cox-dot-net
http://members.cox-dot-net/bluu

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, February 26, 2004 5:34 PM
To: tesla-at-pupman-dot-com
Subject: RE: Gap Question

Original poster: "Luke" <Bluu-at-cox-dot-net>

Ok I see what you are saying.
Thanx
This is starting to click a bit.

This has been a very enlightening topic for me!!

I was used to thinking of resistance as something the hinders the flow
of electricity.  I know that is what it normally means.  But I was not
used to the term being made to refer to the V I properties and not
thought of as actual resistance per say.

And yup I see what you mean in the lower graph the resistance decreases
but the slope does not go negative.

So as well as learning some other stuff here I finally came to grips
with the word resistance in the term negative resistance is not
referring to actual resistance even though the V I can be used to
calculate a resistance.

Thanx.

Luke Galyan
Bluu-at-cox-dot-net
http://members.cox-dot-net/bluu

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, February 26, 2004 7:19 AM
To: tesla-at-pupman-dot-com
Subject: Re: Gap Question

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>

Tesla list wrote:

   > Is it safe to say that a device that displays negative resistance,
   > refers to a components ohmic value decreasing when there is an
increase
   > of voltage or current?  And yes I realize that this would only occur
at
   > certain areas on the V I curve.

Use a fixed-width font to see the pictures.
Negative resistance occurs when the voltage decreases and the current
increases, or when the slope of the i x v curve is negative.

|i         /      |i                /
|         /       |                /
|        /        |               /
|        \        |              /
|         \ here  |      here   /
|          \      |    /\      /
|        __/      |   /  \    /
|     __/         |  /    \  /
|  __/            | /      \/
|_/          v    |/                  v
+-------------    +--------------------

It's not safe to define as Ohmic value i/v. In the negative resistance
region of the curves above it decreases as the voltage decreases, but
it does the same in the curve below, that doesn't have a negative
resistance area:

|i              /
|              /
|             /
|    ________/
|   /
|  /
| /
|/                v
+------------------

So, reserve the term "resistance" for linear resistors, or to measure
the slope of the i x v curve.

Antonio Carlos M. de Queiroz