because plastic is an insulator
Copper wire will undergo plastic deformation even though it does not break like steel wire.
It is not recommended to boil the plastic off copper wire as this can release harmful fumes into the air. It is safer to use a wire stripper or cutter designed for this purpose to remove the plastic insulation from copper wire.
Copper surrounded by a plastic insulator.
The description if that of "coaxial cable".
The copper is a good conductor of electricity. While the insulating plastic covering of the wire prevents bare wires touching and creating a short, or shocking (electrocuting) a person should the bare wire be touched with bare hands.
Coaxial cable
Coaxial cable
Coaxial cable
Plastic, copper wire, silicon chips, and various other materials.
Generally speaking, the copper is the wire. If it is coated, it can be stripped in small sections, but if you need to get rid of a large amount of plastic insulation, you will have to find some safe way to burn it off. Safe, in this context, means in a place where the fumes ( which are toxic ) won't bother anyone, and the metal can be removed without danger- preferably after it has cooled.
Coaxial cable uses an internal piece of copper wire, surrounded by plastic insulation which then has another layer of copper strands before the outer layer of insulation. This is used mostly for radio signals, connecting antennas to things, as well as transferring digital networking signals.
Copper would be the best conductor for the wire to make the bulb brighter, as it allows electricity to flow more easily. Plastic is an insulator and would not conduct electricity, while gold is a good conductor like copper but is less commonly used due to its higher cost.