Re: fallacious filtered white noise

[Bob Sciamanda <trebor@VELOCITY.NET>]

> Yes.  It looks very much like a beating phenomenon.  This system
> has a weak damping, so you are observing a very long transient.  French's
> analysis covers this case.
>
> > with it.  So I presume the differential equation is incorrect.  But I
wonder
> > if it would be possible to design a system for which this differential
> > equation would be correct.
>
> It is actually quite difficult in a mechanical system, as you have
> correctly observed.

When physics students first use a software electronics simulator (PSPICE) to
observe a sinusoidally driven RLC circuit,  they are disturbed by the very
complicated results, most notably when R is small.  This is because their
textbook exposition typically discards the transient and speaks only of the
steady state solution. The simulator shows the complete solution: a
compounding of the transient plus the steady state - this can look very
weird to the discovering student.

Electronics students - used to oscilloscope studies of these circuits - are
equally surprised.
These transient effects are difficult to see in a typical oscilloscope study
of a real circuit, but the PSPICE simulation shows even the fleeting
transient, and holds it for examination.

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
www.velocity.net/~trebor