Comment on Why do so many UK electrical sockets have an on/off switch next to them?
FlyingSquid@lemmy.world 2 months agoI’ve definitely had that happen to me, sort of at random, in the U.S.
But it doesn’t seem to have any effect. It’s not like a gigantic spark and it’s pretty contained.
the_crotch@sh.itjust.works 2 months ago
Oh I’ve never seen that in the US, maybe I just didn’t notice
Fermion@feddit.nl 2 months ago
Laptop power bricks is probably where I see it most. Or if you plug in something with a motor already switched on. Listen for a soft popping noise if you plug in a big power brick.
davidagain@lemmy.world 2 months ago
You’re right, now that I think about it. Laptop power does it more than anything else.
cecilkorik@lemmy.ca 2 months ago
Many, many big power-smoothing capacitors inside those jumping from 0 to 120V in a microsecond, that’s why. The better-smoothed the power supply, the more capacitors and the bigger the sparks tend to be, although some really high quality ones put most of them behind inrush-current limiters to reduce the sparking, but that can also marginally reduce efficiency. High power electronics are always a bit of a tradeoff. The problem is that capacitors charge and discharge almost instantly in most cases, and when empty they act like a short circuit until they’re filled, so they can create some pretty big sparks, even though the actual energy going in is minuscule by any reasonable measurement. It’s almost like a static shock, huge spark, tiny energy.
Some motors will also spark badly when disconnected, but the reason is slightly different. They have a huge electromagnetic field which suddenly fills or collapses and that inductance in the coils can draw a lot of amps on startup and generate some pretty high voltages, more than enough to spark across the gap. Like the capacitors, they are very nearly a short circuit until they start moving.
davidagain@lemmy.world 2 months ago
Home electricity in North America has roughly half the voltage as elsewhere in the world, and double the voltage is double the arcing potential, so that figures.