(1) Copper: yellow
(2) Aluminum: White
You can use a small knife to cut a small slit in the object to see the color inside, if it is white, it is aluminum, if it is yellow, it is copper.
(1) copper: heavy
Copper is denser and heavier than aluminum, and copper transformers are generally heavier than aluminum transformers of the same size
(2) Aluminum: light
An aluminum transformer would be very light
Compare the weight of the transformer with a copper transformer made by the manufacturer.
Of course, we can also roughly identify the weight of the transformer, and the weight ratio between the transformer nameplate and the copper coil transformer sample of other manufacturers can be used as the basis for judgment.
Copper transformer looks fat
Thinner and taller, the overall volume is larger than that of copper core transformers