What causes a small spark in outlet?

robarJune 8, 2013

What causes a small spark when you plug or unplug something from an outlet? It could be any small appliance.....heater.....whatever. I sometimes notice a small spark when plugging in or unplugging......what causes this spark?

Thank you for reporting this comment. Undo
Ron Natalie

Current is still flowing through the plug. When the gap between the plug and the contacts is small enough, even with household voltages, it can span the gap and make an arc. The more current flowing the larger the magnitude of the arc. The duration is diminished the faster you get the plug out.

    Bookmark   June 9, 2013 at 9:21AM
Thank you for reporting this comment. Undo
randy427

When you break a circuit while current is still flowing, the air at the point of the breaking contact tends to ionize enough to support a momentary arc. The higher the current and the slower you remove the plug, the bigger the spark. Electric heating devices tend to draw a relatively high current.
It's best to have the power switch on the appliance turned off before unplugging it, especially on those drawing higher current, in order to avoid the accumulation of high resistance pitting that this arcing causes on the plug and receptacle contacts.

    Bookmark   June 9, 2013 at 9:24AM
Thank you for reporting this comment. Undo
cc_rider

Yep, this is normal, although not necessarily desirable. Every switch, at the moment of contact, makes a tiny spark. The lower the voltage, the smaller the spark. Heck, a 'spark plug' is just a 'switch' that's not quite closed! Jack the voltage up high enough, and that spark will jump across. Pretty handy, but that spark also blasts away a tiny amount of material. Modern spark plugs are made with chi-chi metals that limit the damage. Same for specialty and industrial switches. But if you look inside an old switch, you'll see the contacts are pitted and blackened from the 'damage' caused by opening and closing.

As mentioned, you'll get a bigger spark from an appliance if it is under load. Especially an appliance that heats: toaster, hair dryer, whatever. Heating draws a lot of juice, giving that spark extra energy to jump the gap.

Old, worn-out outlets can spark on their own too, if the contacts have gotten so sloppy the plug doesn't stay in firmly. Another good reason to replace your old two-prong outlets with good three-pronged ones with proper grounding...

    Bookmark   June 9, 2013 at 2:03PM
Sign Up to comment
More Discussions
1 of 2 security light bulbs keep going out, do i need a new light?
I have a security light fixture in my carport that...
tlbean2004
Inspection Report
Had a gorgeous 1909 house inspected yesterday and don't...
cmae17
can homeowner so electrical work in his own home ? (above ground pool)
I live in Western ma and I'm having an Adobe ground...
growingadvice
Troubleshooting Kohler 12RES Problem
I have a Kohler 12RES generator with an RDT 100 Amp...
sniffdog
Humming Transformer
Last summer the POCO replaced the transformer on the...
mike_kaiser_gw
Sponsored Products
Peri Bronze Three-Light Bath Fixture with Amber Matte Glass
$360.00 | Bellacor
Terrene Mercury Blend 1x1 Glass Tiles
$15.95 | TileBar
Basin and Bath Single Lever Mixer With Hand Shower and Bracket
TheBathOutlet
Percy Leather Loveseat - Brighton Energy Pink
Joybird Furniture
Artemide | Tizio Micro Table Lamp
$395.00 | YLighting
Heriz Serapi Red Geometric Design Handmade 8x10 Hand Knotted Wool Area Rug H6977
BH Sun Inc
30" Teak Round Sailor Table
Fifthroom.com
Lite Source Kade Black Gooseneck Desk Lamp with Outlets
$45.00 | Lamps Plus
© 2015 Houzz Inc. Houzz® The new way to design your home™