Does the light bulb have positive and negative poles? Will the wire not light up if it is connected backwards?

Whether the light bulb has a positive pole or a negative pole depends on the power supply. Generally speaking, the power supply can be directly connected to the 220-volt AC power supply, at which time it has no positive and negative poles.

But LED bulbs are divided into positive and negative electrodes. The yellow and red lights can be lit at about 2V, and the rest can be lit at about 3 V. If the reverse voltage is applied too much, the PN junction will be disconnected.

Extended data:

Wiring precautions:

First, prevent electric shock and short circuit.

Second, pay attention to the switch to control the fire line.

Third, it is best not to connect the fuse to the neutral line.

Fourthly, the central part of the lamp holder is connected with the live wire.

Five, don't mix ground wire and zero line.

6. Disconnect the live wire with electrical appliances, so that contact with electrical appliances will not get an electric shock. If the neutral line is broken, people will get an electric shock.

References:

Baidu encyclopedia-firewire