Superconductors and Lenz’s law

Abstract

A superconductor has the unique properties of zero resistance and Meissner effect. Lenz's law is a fundamental law of physics. People have occasionally brought up the question that if a superconductor abides by Lenz's law. There has been lack of an explicit answer to this question so far. Recently, we carried out experiments with superconductor coils and a magnet in search of an answer to this question. We find out that the interacting behavior between a superconducting coil and a magnet does not comply with one of the primary interpretations of Lenz's law: the current induced in a circuit due to a change or a motion in a magnetic field is so directed as to exert a mechanical force opposing the motion. Our experimental results show that the induced current in the superconducting coil do not always oppose the motion of magnet during their interaction. Instead, in a certain portion of the interaction the induced current aids the motion of the magnet. This finding may require the aforementioned interpretation of Lenz's law to be revised as superconductors are involved.

Exploration on the application of a new type of superconducting energy storage for regenerative braking in urban rail transit

“…In the whole energy cycle, the energy can be converted directly from mechanical to electromagnetic then to mechanical without any intermediate equipment, such as motor, generator, and power electronics convertor. Based on the previous studies [6,44], the schematic curve of the force on permanent magnet versus the displacement of permanent magnet is sketched in figure 9. In the figure, the shadow areas visually depict the mechanical energy input/output through the force on the permanent magnet during the energy cycle.…”

Dynamic modelling methodology for an HTS energy converter using moving mesh

“…The specific working process of the HTS energy converter is introduced in [8] in detail. From the perspective of energy, the whole process is divided into two stages, including the PM moving from its initial position, i.e.…”

“…energization of the superconducting devices rather than transfer the energy out of the superconducting devices. Recently, Ying Xin et al found that a permanent magnet (PM) could not only induce but also exploit the persistent current in a closed HTS ring, realizing the conversion of mechanical energyelectromagnetic energy-mechanical energy wirelessly [8]. In this way, the efficiency in energy conversion is enhanced significantly and current leads are avoided.…”

Further study of a novel inductive SFCL for multiterminal HVDC systems

“…Without the SC rings, the magnetic flux produced by the SC coil will enter the iron core, resulting in a significant inductance, which may affect the operation. If the SC rings are installed, induced currents will be generated in the SC rings in the direction to cancel the magnetic flux produced by the SC coil (Lenz's Law) [28]. Thanks to their zero resistance, the flux cancellation could be completed.…”

“…As the inductance of the SC coil contributes the major part of the impedance of the SFCL in the current limiting process [20,28], the inductance of the SC coil can be approximately considered as the impedance of the SFCL. Therefore, the voltage measured across the SFCL can be approximately regarded as the voltage across the SC coil.…”