Whence came this short, sharp shock?
March 26, 2011 3:03 PM   Subscribe

I got a mild shock while putting together a seed starting light set-up in the unfinished basement of my rental apartment. The light was unplugged when I received the shock. What gives?

I am not an electrician, obviously, but I know enough not to mess around with an appliance that's plugged in. I'm mostly just curious, but would also like to know if there is a safety issue I should address here.

Here's the sequence of events.

1. Plugged brand new cheapie fluorescent shop light into basement outlet. I did look around at the wiring before doing so. Nothing looked particularly dodgy to my untrained eye. The wires to the outlet are encased in conduit mounted to the wall; no hanging/exposed wires I could've brushed up against.

2. Noticed that one bulb in the light was sputtering, indicating that it wasn't seated properly in the socket. I unplugged the light to fix this.

3. I'm 99% sure that I did NOT accidentally touch the plug as it was coming out of the outlet, but well after it had been unplugged. There's always room for error but I'm pretty paranoid about that type of thing. Can't tell you which prong I touched. I got a shock that definitely didn't feel like run of the mill static electricity, but closer to a very weak electric fence.

Other possibly relevant factors: I was standing on a dry, concrete/dirt basement floor at the time, wearing slippers with thin rubber soles.

Could the light bulbs have somehow retained some charge after being unplugged? If not, what could have caused the shock and what should I do about it?

Thanks!
posted by Knicke to Home & Garden (6 answers total)
 
If there is a capacitor in the system somewhere then it could have retained a charge.
posted by twblalock at 3:27 PM on March 26, 2011 [2 favorites]


Some fluorescent lights do have capacitors, and that could have done it.
Or just static.
posted by kickingtheground at 3:28 PM on March 26, 2011


I got a shock that definitely didn't feel like run of the mill static electricity, but closer to a very weak electric fence.

Hm, well, static can HURT if it's bad enough. Ever play with a Van de Graaff generator?

Instant-on ballasts have a little bit more going on as they get a very high voltage going initially to get the bulbs to go to full brightness quickly. I'm not exactly sure how they're implemented but it likely involves capacitors of some sort. But with your setup I'm pretty sure that would all be in the fixture, right? And you touched the connectors on the bulb? I'm guessing it was just a little static.
posted by floam at 3:38 PM on March 26, 2011


Condenser. aka ballast, aka capacitor. Fluorescent lights need a boost to get going, this happens with the ballast/capacitor. Capacitors can act as batteries and will hold a charge for a while even if the light is off and unplugged.
posted by plinth at 6:45 PM on March 26, 2011 [2 favorites]


Ah, a capacitor! Fascinating - I had no idea. That must be it. Thanks everyone!
posted by Knicke at 7:08 AM on March 27, 2011


Yes, there is something in those lights that retains electricity. I have a set of those cheap shop lights, and when I turn them off, about 2 minutes later one of the bulbs will flicker.
posted by gjc at 8:04 AM on March 27, 2011


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