Review on Haian Standard Equivalent Voltage Lighting Industrial Electrical by Julie Rodriguez

Since a DC lamp is a light-emitting diode, current can only flow in one direction. While there is no correct polarity rule for an E27 base, it is common for a DC lamp base to be positive and the screw or sides of the base negative. This bulb was reversed and only lit up when positive current was applied to the screws and the base was grounded. This was frustrating because I had to rewire the outlet and mark the bulb with a marker as "Reverse Polarity/Reversal Socket" so I or the next person who walks by doesn't get upset in the future.