Explain why, please. I'm not an electrician, but as I understand it, when you install an electrical socket the same three wires in the romex cable provide power for both plugs. Effectively each of the holes in the top plug is bonded to the same hole in the bottom plug. So why would connecting them with an external wire cause a problem? Even if two outlets are right next to each other, and one has reversed polarity, you'd just be connecting neutral to neutral and hot to hot. I don't understand why it's a fire hazard.

edit: last two sentences are wrong. If one plug has reversed polarity and one doesn't you'd be connecting two wires from hot to neutral, and that would probably just blow a fuse.

[–] glizzyguzzler@lemmy.blahaj.zone 10 points 3 days ago* (last edited 3 days ago)

They’re also often used to connect a portable generator’s 120V outlet to a house’s 120V outlet, thus energizing the house circuit during a power outage. But they have no way to lock in so can fall out and become a naughty cattle prod or if the person forgot to disconnect their circuit breaker from the mains they’ll kill a person fixing the power because that lineperson won’t be expecting live wires.

Basically as you said, if you do everything right you escape with your life. But if you do it wrongk, house fire or murder!

[–] Cheradenine@sh.itjust.works 8 points 4 days ago (1 children)

you are correct, the problem is if you plugged one end into mains that were energized the other end would be live. That can be exciting.

[–] cygnosis@lemmy.world 9 points 4 days ago

hmm. I see. By plugging in only one side you're creating a 120v cattle prod. Yeah, that would be hazardous.

[–] indepndnt@lemmy.world 4 points 4 days ago

In addition to what the other person said, (in the US) if the connection was made between sockets on different circuits, the voltage potential between the two hots could be 240v, making the hot wire a huge heating element, thus the fires.

As I understand it, one typical use case for these things is Christmas lights, and getting confused by a big tangle of light strings makes plugging in both ends in very different places an easy mistake to make.

Also I wouldn't take for granted that your outlets are wired correctly.