Which of the following is the BEST conductor of electricity?

Best electrical conductors (in order, from best): SILVER > COPPER > GOLD > ALUMINUM > tungsten > brass > iron > steel. Silver is the best conductor of all elements, but COPPER is most commonly used in electrical wiring because: silver is too expensive for bulk wire; copper is 95% as conductive as silver, far cheaper, and abundant. GOLD is used where corrosion resistance matters more than ultimate conductivity (connector plating, integrated circuits). ALUMINUM is lighter and cheaper than copper, used in high-voltage transmission lines and some house wiring (though aluminum house wiring has had issues with connector heating). Why metals conduct: free electrons in the outer shell of metal atoms are loosely bound and move freely under an applied voltage. INSULATORS (poor conductors): rubber, glass, plastic, wood (dry), air, distilled water, ceramic, mica. Electrons are tightly bound — current cannot flow easily. Used for wire insulation, switch housings, circuit boards. SEMICONDUCTORS (intermediate): silicon, germanium, gallium arsenide. Conductivity is between conductors and insulators; can be modified by doping with impurities; foundation of all modern electronics (transistors, diodes, ICs, solar cells, LEDs). Resistivity (intrinsic property of material, inverse of conductivity): silver 1.6×10⁻⁸ Ω·m, copper 1.7×10⁻⁸, aluminum 2.8×10⁻⁸, iron 10×10⁻⁸, rubber 10¹³ Ω·m. Wire RESISTANCE depends on resistivity × length / cross-sectional area. Thicker wires (larger area) have less resistance — handle more current without overheating. Long wires have more resistance — voltage drop over distance. Temperature affects conductivity: most metals' resistance INCREASES with temperature; semiconductors' resistance DECREASES with temperature (more electrons gain energy to conduct). Superconductors: certain materials at very low temperatures have ZERO resistance — used in MRI magnets, particle accelerators, some power transmission.