Keith Nagel wrote:
The real joke here is that both Alex and the professor
are talking from textbooks and not from actual experience.
Now wait a minute.
First of all, Alex is still in school. She's not going to have a lot of
real world experience -- cut her some slack!
Second, she's talking to a college prof, in an accademic environment,
and this really is a pretty standard puzzle, used to elucidate various
circuit models. So, of course he's heard of it and knows the "correct"
"theoretical" answer.
Finally, somebody I know conducted a casual poll of engineers around BBN
a long time back, popping this question on them. The only one who
_immediately_ got the "right" answer was an aging hardware engineer with
lots of hands-on experience. The young guys shortly out of college who
never touched anything that wasn't digital gave answers along the lines
of "uuuhh -- golly, you can't, can you..." Sure, it's just a gedanken
experiment, but none the less a lot of engineers have chuckled over it
at one time or another.
'Course it was that same engineer who fixed the power supplies on some
set of IMPs so the machines would work in Europe. When asked how to
tell if a particular IMP had the fix, he said, "Just listen to it when
you turn it on. If it doesn't go 'thwong' it's fine."
No test equipment manufacturer sells an ideal current source.
What you can actually build or buy, are constant current
sources. Real constant current or contant voltage
source can be told apart with nothing more than a RatShack
multimeter. Short both, and see which one is still working
after driving the dead short. Amusingly enough, you could
tell from the temp rise that the _voltage_ source is the
hotter one, if it doesn't fail or explode.
Sure, but the "touch them" answer is given with the assumption that
they've both just been sitting there on the lab bench for a while.
Mistake piled
on mistake. It made me laugh, that's for sure, so it's
a good comic anyway.
Then there was that old story told to undergrads, of the box found in
the college basement, labeled "1 amp, no matter what"...
K.
-----Original Message-----
From: Jed Rothwell [mailto:[EMAIL PROTECTED]
Sent: Wednesday, May 10, 2006 12:02 PM
To: [email protected]
Subject: OFF TOPIC "Doonsbury" features calorimetry
And Cornell! See:
http://www.doonesbury.com/strip/dailydose/index.html
It's not often you see "Thevenin and Norton equivalences" in a comic strip.
- Jed
