Experiments
Latest change
2024-11-28
In brief:
Several experiments have been done or are planned, in an attempt to find the cause of certain behaviour.
The main issue is of course the way the elliptical path grows, is limited, and alternates in rotational direction.
As my pendulum does not have any explicit means to limit ellipse growth
(Charron
ring, Eddy current damping, etc) and has elaborate methods of measuring
and logging it's behaviour, it forms a attractive vehicle to do such
experiments.
Experiment "Kick the Ellipse"
The "normal" behaviour of my pendulum is that it follows an elliptical
path with an alternating direction. Moreover, the directional changes
seem to be synchronized with the N-S and E-W transitions of the foucault
plane. Consistently the ellipse direction is CW in the first an third
quadrants and CCW in the second and fourth quadrant.
In these experiments I kicked the bob to the "wrong" direction, and watched it return to the "good" direction.
I think it is worthfull to note the time constant involved, that may tell us something about the underlaying mechanism.
To the experiment....
Experiment "Free Run and kick"
This test was initilly done to find the Q of the pendulum. I just
disabled the drive pulses and watched the amplitude to decay.
Even if the test was done at a moment of no noticable ellipse, an elliptical path evolved.
Kicking that ellipse to the other direction did not result in returning to the original direction.
Obviously the mechanism that lets the ellipse return to its "original"
direction in the "Kick Elliopse" experiment is now absent.
To the experiment....
Experiment "Rotate Top Unit and Rotate Floor Unit"
In the literature about Foucault Pendulums the origin of the elliptical
path is almost universally attributed to anisotropy in the construction
of the pendulum, and/or influences from the environment: air flow,
magnetic fields, name it. But I've seen hardly any experimental evidence
supporting this statement.
I did these experiments on suggestion of prof. Schumacher.
Rotating the TopUnit (that is including the wire clamp, the magnet and
the Hall sensors) did not convincingly change the phase of the
elliptical alternations.
The same is found for rotating the Floor Unit with the drive- and sense coils.
To the experiment....
Experiment "Magnetic fields"
As we all know we live on Magnet Earth. The Geo Magnetic Field (GMF) is
omnipresent, and I use magnets in my pendulum for driving and measuring.
In NL the horizontal component of the GMF is quite well aligned with the
geographical North, so I cannot make a clear difference between
magnetically induced effects and effects of the earth's rotation. So I
did some experiments with an externally applied magnetic field.
A special set of colis
was made, which allowed me to produce a magnetic field of any direction
and
strength up to a few times the local GMF.
Only when the extra field was pointing up or down effects were seen, and
these effects reversed when the magnet in the bob was reversed.
To the experiment....
Experiment "Air flow"
A few simple tests with a household fan and a much smaller fan proved that a sytemic air flow is disastrous.
Also switching on the house heating had a serious effect.
To the experiment....