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Re: Alternating Current



On Fri, 29 Jan 1999, David Abineri wrote:

I just did a lab today with my Pre Calculus class. Since we have
introduced sinusoidal variation I had them use a CBL to look at the
light intensity from an incandescent bulb sampling every .0001 seconds
for 100 data points.

When one does this, the calculator shows a beautiful sinusoidal graph
and the regression analysis shows an excellent fit with supporting
residuals.

However, I would have expected to see a graph more like |sint| which
should not look like a sin but should have the frequency of double the
line voltage frequency since each half of the voltage cycle produces a
full cycle of light intensity. The frequency came out consistently at
124Hz by the way and I wonder if the power company is typically this far
off their standard value of 2*60Hz?

Not likely, or your electric clocks would be running a bit fast. They try
to keep the line frequency accurate to a fraction of a percent.

Can anyone help me with this? Am I really seeing |sint| and it just
looks like sint? Has anyone else tried this?

Thanks for the help.
--
David Abineri dabineri@choice.net


Thermal heating likely can't support higher frequencies of the temperature
variation of the filament, therefore effectively "filtering out"
everything but the 120 Hz.

-- Donald

.....................................................................
Donald E. Simanek
dsimanek@eagle.lhup.edu http://www.lhup.edu/~dsimanek
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