In most circumstances and electrical schematics L1 is black and L2 is white. L1 is usually the "hot" wire and L2 is the "neutral".
If both wires are black, the one that connects to your white wire is the one that should have little writing on it. Black to the plain black wire, white to the wire with writing.
Wall receptacles are wired in parallel. black to black, white to white, ground to ground.
the black wire is the hot wire
In a household circuit, with a "hot" conductor insulated black and a white neutral, the black wire should connect to the center terminal of the socket. The outside part of the socket usually has a brass screw (for the black wire) and a nickel screw (for the white wire).
In typical American wiring the black wire on an outlet goes to the gold (copper) screw and the white wire goes to the silver screw. The ground wire goes to the green screw.
L1 is black or the hot wire and L2 is white or the netural wire
The last fixture in a parallel circuit is wired the same as the first. In North America, all of the fixtures are wired black wire to black wire and white wire to white wire. The black wire being the "hot" wire and the white wire being the neutral wire.
if it is a 240volt motor it does not matter,
Black Wire from photocel to hot wire(black) coming in red wire to light fixtures black wire. White wire to neutral wires all light and power source white.
If you are asking about the electrical cord on a lamp, the black wire with the white stripe is the neutral conductor.
If both wires are black, the one that connects to your white wire is the one that should have little writing on it. Black to the plain black wire, white to the wire with writing.
you dont
white wire = neutral bare wire = ground black wire = line voltage red wire = returned from a switch, or the other phase of line voltage in order to supply 240VAC
black
The white is neutral. The house does have a neutral wire even though it may be black. One of those black wires is the neutral and the other is the hot wire. You will have to determine which is hot and which is neutral. You can easily do this with a voltage tester. The wire that lights the tester is the hot. When you wire the light simply wire the hot to hot, and the white and green to the other wire.
Wall receptacles are wired in parallel. black to black, white to white, ground to ground.
The ribbed wire on a lamp cord is the neutral wire. On an extension cord there is no rib but the neutral wire is white in colour.