Magnetic levitation

Magnetic Levitation

磁悬浮

Magnetic fields are actively excluded from superconductors (Meissner effect). If a small magnet is brought near a superconductor, it will be repelled becaused induced supercurrents will produce mirror images of each pole. If a small permanent magnet is placed above a superconductor, it can be levitated by this repulsive force. Levitation currents in the superconductor produce effective magnetic poles that repel and support the magnet. The black ceramic material in the illustrations is a sample of the yttrium based superconductor.

磁场被主动排斥出超导体（迈斯纳效应）。如果将一个小磁体靠近超导体，它会被排斥，因为感应超电流会产生每个极的镜像。如果将一个小的永磁体放在超导体上方，它可以通过这种排斥力被悬浮。超导体中的悬浮电流会产生有效的磁极，这些磁极排斥并支撑着磁体。图中黑色陶瓷材料是一种基于钇的超导体样本。

By tapping with a sharp instrument, the suspended magnet can be caused to oscillate or rotate. This motion is found to be damped, and will come to rest in a few seconds.

通过用尖锐的工具轻敲，悬吊的磁体可以被使其振动或旋转。这种运动被发现是阻尼的，几秒钟内会停止。

Levitation Currents

悬浮电流

The Meissner effect in superconductors like this black ceramic yttrium based superconductor acts to exclude magnetic fields from the material. Since the electrical resistance is zero, supercurrents are generated in the material to exclude the magnetic fields from a magnet brought near it. The currents which cancel the external field produce magnetic poles which mirror the poles of the permanent magnet, repelling them to provide the lift to levitate the magnet.

The levitation process is quite remarkable. Since the levitating currents in the superconductor meet no resistance, they can adjust almost instantly to maintain the levitation. The suspended magnet can be moved, put into oscillation, or even spun rapidly and the levitation currents will adjust to keep it in suspension.

超导体的悬浮过程相当显著。由于超导体中的悬浮电流遇到的电阻为零，它们可以几乎立即调整以维持悬浮状态。悬浮的磁体可以被移动、产生振荡，甚至快速旋转，而悬浮电流会调整以保持其悬浮。

在像这种黑色陶瓷钇基超导体这样的超导体中，迈斯纳效应的作用是将磁场所排除在外。由于电导率为零，当靠近它时，超导体中会产生电流以排斥接近的磁体的磁场。这些抵消外部磁场的电流会产生与永磁体磁极相镜像的磁极，从而排斥永磁体，提供升力以使磁体悬浮。