Re: An ohmic experiment

["Paul O. Johnson" <pojhome@FLASH.NET>]

Michael Edmiston wrote:

> I mentioned, in a previous message, that I have students plot I versus delta-V for
> resistors over a range of power sufficiently high that they nearly "smoke" the
> resistors.  Then I have them repeat the experiment over the same power range, but with
> a heatsink.  I have them do this with both a nichrome resistor and with a carbon-film
> resistor.  There are some neat things that result from this.
>
> (1) The I versus delta-V plots for both types of resistors show slight non-linear
> behavior when the resistors are allowed to heat-up.  They both display very linear
> behavior when fitted with a heatsink and plotted over the same range as without the
> heatsink.  This demonstrates the non-linear behavior was temperature induced and not
> voltage induced.  That means these are actually behaving as ohmic materials.

That's as clear an answer as I've ever gotten. Thanks, Michael. Now, let's generalize a
bit. Aside from the intentionally non-ohmic devices that have been mentioned in this
thread, are most substances (homogeneous elements and compounds) ohmic in the sense of
your result (1)?

poj