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A
levitation device based on the use of several
ceramic magnets has been developed to demonstrate that
levitation can be achieved using a single thread
to vertically secure a levitated magnetic device from below while the
levitated magnetic device is also being supported from below using the mutual
repulsion of opposing magnetic fields.
It is simple to achieve levitation using a
single thread to secure a levitated magnetic
device from
below while it
is also being supported from above using another
magnet of opposite polarity. However, using a
single thread to vertically secure a levitated magnetic
device from
below while the levitated magnetic device is also being
supported from below requires the levitated device
to
be located in a uniform magnetic field of
opposing polarity. In the design presented below the
bottom-mounted thread is used to "pull" the
levitated upper magnet into the potential well of
the support magnetic field located below. If the
levitated magnetic device drifts into the negative curvature
portion of the support magnetic field the levitated
magnetic device will tip over and become unstable. The split
design of the support
magnetic field device provides a larger potential
well for the levitated magnetic device resulting in greater
overall stability.
To assure the levitated magnetic device is located in the
potential well of the support magnetic field a mechanism to position
the thread support-point relative to the center of
the split support magnets is illustrated below. The upper
Plexiglas plate is positioned and secured
using two cap screws until the levitated magnetic
device
is centered and stable. In this configuration the
levitated magnetic device is stable and will not crash even while carrying the system from
place to place.
Levitation without the physical constraint of a
bottom-mounted thread is possible if the levitated
magnetic device is allowed to rotate like a top and if the proper amount
of ballast or weight is added. The precession or
gyroscopic action of the spinning magnetic device provides sufficient flipping resistance (torque) to prevent
the top from overturning and aligning north to south
with the base magnet. Also, the ballast acts to push
the top into the potential well of the support
magnet where the magnetic lines of force are
optimum. As an example of this technology the Levitron
Anti-Gravity Top
achieves levitation without external constraint by using gyroscopic
precession to counter the torque engendered by
opposing magnetic fields and weight adjustments for optimum vertical top
placement within the support magnetic field. However, gyroscopic levitation is a
challenge to achieve and difficult to maintain
because of temperature related effects on
magnetic field strength. A totally new product
called the Levitron
Anti-Gravity
Globe overcomes the Earnshaw theorem constraint
problem by using an
electronically controlled electromagnet to properly
position the levitated object within the support
magnetic field but time varying magnetic fields not
static magnetic fields are used to achieve
levitation. The electronic kit provided by this link
shows how levitation is achieved using a linear
Hall effect sensor combined with an electromagnet to
levitate a very small device containing one or more rare
earth magnets. However, this article admits the
technology is not scalable to larger sizes.
The object of this work is to remove as
many constraints (degrees of freedom) as possible
from the levitating magnetic device without violating Earnshaw's theorem.
Earnshaw's theorem states
that no static arrangements of magnetic or electric
charges can be stable, alone or under gravity. More
information on the use of static magnetic fields to
achieve levitation using a minimum number of
constraints will be posted here as work
continues... |