Re: CUBE RESISTANCE

["John S. Denker" <jsd@MONMOUTH.COM>]

Chuck Britton wrote:

> I am AMAZED that JSD doesn't know how to build a circuit that uses a
> common OpAmp ;-)
>
> Or MAYBE JSD was just exercising a bit of hyperbole.

Or... maybe there's something else going on.

Learning proceeds from the known to the unknown.
When I am addressing (directly or indirectly) a
bunch of high school students, it doesn't matter
how much I know about op amps;  it only matters
how much _they_ know.

> Symmetry, yes. But don't minimize Bernie's "Virtual" connection idea.
>  OpAmp users make use of the 'virtual ground' abstraction every day.

As a grader, I would be happy to accept a solution
using "virtual" node voltages.  The rule is, you can
solve the problem using any techniques you can scrounge
up.

As a high-school teacher, I don't think I would teach
it that way.  Learning proceeds from the known to the
unknown.  Op amps (and the associated feedback principles)
are fine things, but they're not on any AP physics syllabus
I've ever seen.