Superconductors

A magnet levitates above a superconducting material

A superconductor is an element, inter-metallic alloy, or compound that will conduct electricity without resistance below a certain temperature. Resistance is undesirable because it produces losses in the energy flowing through the material. Once set in motion, electrical current will flow forever in a closed loop of superconducting material--making it the closest thing to perpetual motion in nature. In the image below, a magnet is levitated on a superconducting material.  

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