Explaining Eddy Currents in Maglev & Levitation Expts

[chanderjeet]

Can someone explain the role of eddy currents that produce levitation such as in the floating tube expt or the jumping ring? How is the jumping ring altered to achieve stability? i.e raising the ring a fixed distance above the coil? Like in maglev transportation...or is it just dependant on the strength of the magnetic field?

 

[Bob S]

You have not given us a fuller description of the eddy current "jumping ring" or "floating tube", but based on my experience with eddy currents, the force comes about because of the inducing magnetic field B interacting with currents produced by the inducing dB/dt in conductors. The force is in a direction to push the conductor (conducting loop) to a region of lower B and dB/dt. This is (was) the basis for the popular repulsion-start single-phase electrical motors manufactured up until about WW II.

I have seen sheets of aluminum in 500-Hz oscillating vertical magnetic fields (+/- 2000 Gauss) align along the field lines to minimize the energy loss (heat dissipation).
Bob S

 

[sir-pinski]

Eddy currents are a type of electrical current that is induced in a conductor when it is exposed to a changing magnetic field. In the context of maglev and levitation experiments, these currents play a crucial role in producing the levitating effect.

In the floating tube experiment, a tube made of non-magnetic material is placed above a set of powerful electromagnets. When the electromagnets are turned on, they create a changing magnetic field that induces eddy currents in the tube. These eddy currents then create their own magnetic field, which interacts with the magnetic field of the electromagnets. This interaction results in a repulsive force between the two magnetic fields, causing the tube to levitate above the electromagnets.

Similarly, in the jumping ring experiment, a ring made of non-magnetic material is placed above a coil of wire. When a current is passed through the coil, it creates a changing magnetic field which induces eddy currents in the ring. The interaction between the magnetic fields of the coil and the eddy currents causes the ring to jump and levitate above the coil.

To achieve stability in these experiments, the distance between the conductor (tube or ring) and the electromagnet or coil must be carefully controlled. This is because the strength of the eddy currents and the resulting repulsive force are dependent on the distance between the conductor and the magnetic field. By raising the conductor a fixed distance above the magnetic field, the strength of the eddy currents can be controlled, thus achieving stability.

In maglev transportation, the strength of the magnetic field is also a crucial factor in achieving levitation. The stronger the magnetic field, the greater the repulsive force between the magnetic fields of the train and the track. However, other factors such as the design of the train and track also play a role in achieving stability and maintaining the levitation effect.

In conclusion, eddy currents play a vital role in producing levitation in maglev and levitation experiments. The stability of the levitation can be controlled by adjusting the distance between the conductor and the magnetic field, and in maglev transportation, the strength of the magnetic field is an important factor.