الفهرس 
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Abstract
A perfect superconductor is a material that exhibits two characteristic properties namely zero electrical resistivity and perfect diamagnetism whem it is cooled below a particular temperatura called the superconduction transition temperature tc as shown in figure at higher temperatures it behaves like a normal metal and ordinarily is not a good conductor for example lead tantalum and tin become superconductors at tc=7.2 k 4.47 k and 3.7 k respectively on the other hand copper silver and gold which are much better conductors do not become superconductors in the normal state above tc some superconducting metals are weakly diamagnetic and some are paramgnetic.