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Re: There's work, and then there's work



Dear David:
The only equipment you need is a common voltmeter;
I am sure your local college will let you borrow it. They
will also give you a resistor; it costs them ~ $0.1 or so.
A closed styrofoam cup, and a common thermometer,
will do for a calorimeter, in your context. Where is
your school located, David? Perhaps somebody from
this list, who is near by, will help. Your students are
likely to benefit from this.
Ludwik


On Tuesday, Jan 28, 2003, at 14:02 US/Eastern, David Rutherford wrote:

Ludwik Kowalski wrote:

On Tuesday, Jan 28, 2003, at 11:52 US/Eastern, David Rutherford wrote:


I was hoping to get an answer to this question. Is it valid to
combine
(add) the results of both experiments if they are done at the same
time
on the same circuit? If not, why not?

You are correct that two experiments can be performed at the
same time. I would suggest one modification. But be careful
that your galvanometer, if that how you measure i several
times while a large capacitor discharges, has an R2 that is
very small in comparison with the R1 inside the calorimeter.
On the other hand, too large R1 and too large C can lead
too long cycles; you want to finish the experiment faster
than too much heat escapes from the calorimeter.

You can avoid this dilemma by not using a galvanometer.
Measure U on the capacitor (same as on R1) with a voltmeter.
Then calculate instantaneous i=U/R1. The impedance of the
voltmeter should be much larger than R1. This will not be
hard to satisfy with a common instrument. An oscilloscope
with memory is also a possibility (to record U, for example,
every two seconds) but such instruments are not common.

But do not forget that other contributors to this thread are
going to wait for the experimental resolution of your
dilemma. Do not disappoint us.

I don't have the equipment or the money to buy it, so I'll have to try
to convince someone at a local college to help me do the experiment. As
I'm sure you know, that won't be easy. If someone else would like to
try
it, go ahead, and report your results, here, along with the details, so
that others can try to reproduce your results.

--
Dave Rutherford
"New Transformation Equations and the Electric Field Four-vector"
http://www.softcom.net/users/der555/newtransform.pdf

Applications:
"4/3 Problem Resolution"
http://www.softcom.net/users/der555/elecmass.pdf
"Action-reaction Paradox Resolution"
http://www.softcom.net/users/der555/actreact.pdf
"Energy Density Correction"
http://www.softcom.net/users/der555/enerdens.pdf
"Proposed Quantum Mechanical Connection"
http://www.softcom.net/users/der555/quantum.pdf