 The material composition and cross-sectional size of the busbar determine the maximum amount of current that can be safely carried.Busbars can have a cross-sectional area of as little as , but electrical substations may use metal tubes in diameter () or more as busbars.An aluminium smelter will have very large busbars used to carry tens of thousands of amperes to the electrochemical cells that produce aluminium from molten salts.