Re: Gap Question

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

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