While Enameled Copper Wire is heavier than Enameled Aluminum Wire, it is often used to make smaller and lighter transformers.  This is because copper offers higher electrical conductivity levels than aluminum. The resistivity of copper is 0.6 times that of aluminum. Therefore, the cross-section of an aluminum conductor needs to be 1.66 times larger than that of a copper conductor to demonstrate the same amount of resistance. As a result, an aluminum wound transformer would need to be much larger than a copper wound one to handle the same load.

Some of the other advantages copper wiring offers over aluminum wiring include:
Lower losses (due to better electrical conductivity) and temperatures (due to better thermal conductivity)
Greater reliability with regard to line and load connections
Better manufacturability since the generally smaller-diameters conductors are easier to handle

●Coils are typically wound with enameled copper wire, sometimes termed magnet wire.
●The winding material must have a low resistance, to reduce the power consumed by the field coil, but more importantly to reduce the waste heat produced by ohmic heating.

The enameled wire basically refers to an aluminium or copper wire which has been given a coating. 
This thin layer of insulation mates it useful for building transformers, motor, inductors, hard disk actuators,
speakers, electromagnets, etC.
The enameled copper wire is electrolytic - refined copper.
Since these wires come with a coating they are also popularly called magnet wires.
●This type of copper wire is most extensively used in constructing transformers and motors.
●It finds use in the application which needs insulated wires that are tightly coiled.
●The main reason for using this coating or 'enamel' is to prevent the wire from getting caught in accidental short circuits.
●The enameled copper wire is also useful because it can be soldered easily.
●Magnet wires will produce electromagnetic fields if one winds them to create coils; these get reenergized in the process.
●The enameled copper wire is used to convert electrical energy to mechanical energy for making motors, office HVAC, etc.
●The main reason for using copper is because of its high electrical conductivity.
●So the use of this metal (Cu) as compared to other types of metals is more because it improves energy efficiency for motors.
●Thus enameled copper wire is used for generator, motor winding, and field windings.

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