I am working in an Auto Parts manufacturer company which one of its production is DC motors used in different wheicles. I have two type of question about a DC motor : 1: we have a new model DC motors which get too hot. whats the reason? what does the effect of the thickness of cooper wire of armature ? if we want to reduce the Current can we use more thicker wire in armature? whats the effect of thicker wire on RPM?whats the effect in number of wounded wire? does they related to RPM? would you guide me by equations and formulas too? 2: our DC motor have 2 speed. high and low. we use a resistor to provide multiple speed. is there any other way to produce multiple speed beside resistor?