Re: R = V/I ?

[Jim Green <JMGreen@SISNA.COM>]

I must confess that I continue to be confused by this thread -- maybe I am
just amused.

Some people are saying things like the following::

> What *I* say is that unlike the resistance of a resistor,
> the resistance of a light bulb is not a constant.
> It is then interesting to measure the resistance of both
> & confirm this.

And others say things like this:

> ... it is not appropriate to describe light bulbs by their resistance
> as they do not behave like resistors. A VI characteristic is
> necessary to describe their behaviour in circuits. ...

What I don't understand is that both are really saying the same things --
as the light bulb filament heats up its resistance changes and half the
list gets all atwitter,

The other halve pictures a common circuit  "resistor" and attribute a
"resistance to _it_ -- even while current is flowing through it -- and they
mistakenly think that the resistance remains constant.

BOTH elements  have I^2R-like  losses and "heat" up -- and their
"resistance" changes.

This phenomenon occurs in ALL simple circuit elements which pass current:
common resistors, compensating resistors, diodes, Zeners, transistors.
inductors, capacitors (with ac), light bulbs, batteries, etc, etc, etc
.........

The object in any conversation is to agree on the usage of words and use
them!  But for heaven's sake don't try to learn physics in a dictionary!

Somebody please explain to me all the hoopla.


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen