You will also see black wires as internal wiring in light fixtures and ... (wires without an insulated covering) in electrical boxes are “ground” wires, more appropriately called equipment ...

The ground wire is what's missing in a knob and tube electrical system," added Ticknor. Another clue are the outlets. Knob and tube wiring has two prongs outlets, not three. In some knob and tube ...

The case becomes an extension of that live wire. This is called a fault. But the metal case is connected to an electrical path consisting of the ground wire in the power cord plugged into the ...