A live wire is a wire that carries electrical current from the source to a switch or appliance. It is also known as the "hot" wire because it carries a high voltage and is always carrying an electrical current as long as its connected to the power source. The live wire is typically colored brown in UK plugs, replacing the old color of red. It is important to note that live wires are dangerous and should be treated as such, even if they are not actually live. If you come across an exposed wire, it is best to deal with it immediately and avoid contact with it.