Notes on Magnetic Levitation
This is a stub to keep a link to the interestingengineering.com‘s article on spinning magnet levitation:
“Physicists have deciphered the underlying physics of a perplexing “magnet levitation” phenomenon first reported by a Turkish researcher in 2021.
The phenomenon involves the levitation of a nearby magnet caused by the fast rotation of another magnet, which challenges traditional physics.
A series of experiments carried out by researchers at the Technical University of Denmark revealed how a spinning magnet may produce levitation in a secondary magnet without requiring stability.The perplexing phenomenon
The 2021 experiment entailed coupling a magnet to a quickly spinning motor, which caused a nearby second magnet to hover unexpectedly. While magnetic levitation is a well-known concept, this specific instance perplexed researchers since it defied traditional physics laws.
Rasmus Bjørk, a professor at DTU, was intrigued by the experiment and decided to reproduce it.
“Magnets should not hover when they are close together. Usually, they will either attract or repel each other. But if you spin one of the magnets, it turns out, you can achieve this hovering. And that is the strange part,” Rasmus Bjørk, who led the new study, said in a press release.
Bjørk further explained: “The force affecting the magnets should not change just because you rotate one of them, so it seems there is a coupling between the movement and the magnetic force.”The extensive series of experiments
In this recent study, the team attempted to replicate the 2021 experiment for a more in-depth understanding.
The researchers combined various types of magnets and set them in motion at varied rates.
The researchers saw a second magnet, known as a “floater magnet,” spinning at the same speed and stabilizing into a hovering posture as a result of a magnet’s rapid rotation.
Reportedly, they recorded the events using high-speed cameras and motion-tracking software, allowing them to determine the underlying reason for this unusual occurrence.
In contrast to anticipated outcomes from magnetostatics, the floater magnet positioned itself near the axis of rotation and toward the same pole as the rotor magnet.
To gain a deeper understanding of the phenomenon, the researchers created a simulation that allowed them to control the interactions between the two magnets.
During the simulation, they discovered that the magnetic field of the rotor magnet imparted torque to the floater, forcing both magnets to revolve simultaneously owing to the gyroscopic effect. It is a phenomenon related to the behavior of spinning objects.
However, the floater exhibited a slight resistance, leading to the formation of a parallel arrangement.
Furthermore, a tiny misalignment in the rotor magnet’s polar axis relative to its magnetic field resulted in a balance of attracting and repulsive forces, allowing the floater to maintain a constant position while levitating.
“It turns out that the floater magnet wants to align itself with the spinning magnet, but it cannot spin fast enough to do so. And for as long as this coupling is maintained it will hover or levitate,” said Bjørk.
The study was published in the journal Physical Review Applied.
Study abstract:
A permanent magnet can be levitated simply by placing it in the vicinity of another permanent magnet that rotates in the order of 200 Hz. This surprising effect can be easily reproduced in the laboratory with off-the-shelf components. Here, we have investigated this novel type of magnetic levitation experimentally and clarified the underlying physics. Using a 19-mm-diameter spherical Nd-Fe-B magnet as the rotor magnet, we have captured the detailed motion of levitating spherical Nd-Fe-Bmagnets, denoted floater magnets, as well as the influence of the rotation speed and magnet size on the levitation. We have found that as levitation occurs, the floater-magnet frequency locks with the rotor magnet and, noticeably, that the magnetization of the floater is oriented close to the axis of rotation and toward the like pole of the rotor magnet. This is in contrast to what might be expected by the laws of magnetostatics, as the floater is observed to align its magnetization essentially perpendicular to the magnetic field of the rotor. Moreover, we have found that the size of the floater has a clear influence on the levitation: the smaller the floater, the higher the rotor speed that is necessary to achieve levitation and the further away the levitation point shifts. Despite the unexpected magnetic configuration during levitation, we have verified that magnetostatic interactions between the rotating magnets are responsible for creating the equilibrium position of the floater. Hence, this type of magnetic levitation does not rely on gravity as a balancing force to achieve an equilibrium position. Based on theoretical arguments and a numerical model, we show that a constant vertical field and eddy-current-enhanced damping are sufficient to produce levitation from rest.” [1]