NetNews Usenet Archive 1992 #26/NN_1992_26.iso/spool/sci/physics/fusion/2650

Text File | 1992-11-10 | 3.7 KB | 68 lines

Newsgroups: sci.physics.fusion
Path: sparky!uunet!news.tek.com!uw-beaver!news.u.washington.edu!news.uoregon.edu!cs.uoregon.edu!sgiblab!pacbell.com!UB.com!zorch!fusion
From: Jed Rothwell <[e-mail]>
Subject: Notoya's mistake, distorted
Message-ID: <[e-mail]>
Sender: [e-mail] (Scott Hazen Mueller)
Reply-To: Jed Rothwell <[e-mail]>
Organization: Sci.physics.fusion/Mail Gateway
Date: Wed, 11 Nov 1992 01:02:09 GMT
Lines: 56

To: >INTERNET:[e-mail]

Douglas Morrison posted a twisted version of the mistake found in Notoya's
light water cell demonstration:

"Steve challenged [David] to measure the resistance of the control cell leads
somehow. David moved the alligator clips from the ends of the thin lead wires
to points where the leads entered the control cell. He saw that the voltage
dropped and from this determined that the thinnest lead had a high resistance
so that the wire must have been quite thin. He estimated that half the power
delivered to the control cell was dissipated in the air, not in the solution
which would make it appreciably cooler than the other cell. The demonstration
was removed before the end of the conference."

David moved the alligator clips on the right hand silver wire near the top.
Immediately after that, Dr. Notoya and I moved both clips the rest of the way
up. She also measured the resistance again. She said, "oops, it is greater
than I thought." She adjusted the current to account for the resistance, and
the temperature in the dummy cell went up only about a degree. So clearly
David was wrong, "half the power delivered to the control cell" was *not*
dissipated into the air, because when we reduced the length of the silver lead
by about half (leaving most of the wire underwater), the dummy cell remained
14 degrees cooler than the CF cell.

The demonstration was removed just before the end of the conference by Dr.
Notoya and I. We packed up the power supplies and other equipment in large
boxes, and called in a delivery service to ship it back to Hokkaido
University. She could not have carried all that stuff in a Taxi! Dr. Notoya
will bring the cells to the U.S. in a few weeks, tentatively to Stanford
University in the last week of November, and definitely to M.I.T. around
December 1 or 2. Anyone who wishes to measure the resistance of the silver and
platinum leads will be more than welcome to do so. You do not have to measure
it "somehow;" it is not "a challenge."  You can bring your own meter, or
borrow Dr. Notoya's.

Dr. Notoya plans to replace the thin silver wire with a heavier gauge one, and
she will measure resistance very carefully this time, she promises.

I like my version of this story a lot better than Morrison's. No mysteries
here. Nobody "doing their best to measure things" by some seat of the pants
method. Nobody "removing demonstrations" before the end of the conference and
vanishing into the night. Let me re-emphasize that this was a "walking around"
demo and NOT, by any means, a full scale, scientific experiment. Notoya has a
full scale experiment back in the laboratory which is much more convincing,
because she uses a proper calorimeter, thermocouples, a much shorter (3 cm)
and heavier gauge silver wire, and she measures the gas from electrolysis.

Notoya did make a minor error measuring the resistance of a wire, but perhaps
Dr. Morrison will cut her a little slack here, since we all make mistakes from
time to time. Dr. Morrison certainly made a foolish error when he noted Dr.
Buehler's comments, jumped to the conclusion that Buehler was right, and never
bothered and verify whether the temperature of the dummy cell had actually
gone up 15 degrees or not.

- Jed