Question

why does an electric copper wire develop a thin black coat on it

Answer 1

$<b>Explanation$:-

✔️Electrical copper wire developer thin black coat on it because metal good conductor of electricity while the plastic
✔️Rubber is a bad conductor of electricity which we used like a thin black coat on the electrical copper wire to protect from electric shock

Answer 2

Answer:

bcoz it get oxidised

2Cu +O2 -> 2CuO