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What Causes an Outlet to Spark?

Standard U.S. power outlet.
Fuses in a fusebox.
A glass fuse.
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  • Written By: Michael Pollick
  • Edited By: Niki Foster
  • Last Modified Date: 07 April 2014
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    Conjecture Corporation
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Sometimes, when you plug an electrical appliance into an outlet, you may notice a small blue spark. In most situations, this is a normal event as the electrons begin to flow into the appliance's power cord. At other times, however, a spark from an electrical outlet could start a fire or severely damage the plug. It is important for homeowners to understand why an electrical outlet may spark or short out without warning.

The electricity that powers a home comes in through a supply line connected to the main electrical grid. In countries like the United States, this supply line carries electricity at approximately 115 to 120 volts, with an average frequency of 60 hertz, or 60 cycles per second. In other words, the electricity flowing through the circuits of your home is running very fast and hot. Ideally, it should flow through the circuit and back out to the main grid without much interruption.

The electrical outlets in your home essentially tap into this fast-moving electrical stream and divert some of the electricity to whatever you plug into them. The electricity runs through one slot of the outlet, powers the appliance, then escapes through the second slot of the outlet. Any spark you may notice on the 'hot' side of the outlet is usually caused by the appliance's sudden draw of amperage. Once the electrons begin to flow, the spark dissipates, much like static electricity.

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Once in a while, however, the relationship between the outlet and the two circuit wires becomes problematic. Electrical power can also cause heat energy, and this excessive heat can cause the insulation around wires to melt away. Once an electrical wire becomes exposed, it can come into contact with the metal casing of the outlet or even with the other circuit wire. If a connection is made, electrons leap across the gap and form a visible spark. Since the connection shortens the intended distance of the circuit, it is frequently called a short or short circuit.

A short circuit caused by overheated wiring can not only cause an outlet to spark - it can also create the ignition source for a dangerous electrical fire. Ideally, any short circuits should trigger a breaker switch or overload a fuse within a few seconds. Once the circuit has been broken, the electricity should stop flowing and the risk of fire should be reduced. If the household wiring is faulty, however, the entire circuit could overheat and create a fire behind the walls. This is why homeowners need to watch for any spark from their electrical outlets, particularly when running a number of appliances on the same circuit.

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Discuss this Article

anon353673
Post 27

I have the same question as johnson post 2, except with VCRs.

anon348498
Post 25

@anon337576: I'm not a electrician myself, but it seems like the tester should have lit up if you still have electricity flowing through the socket. No light at all suggests a short or a break in the circuit to me. If that's the case, I wouldn't try plugging the appliance back in until someone checks the entire circuit, including the internal wiring and the fuse box/breaker box. Most sparks I've seen when a plug goes into a socket are blue in color, so yellow doesn't seem normal, either. If I had to guess, I'd say the socket itself isn't properly grounded, so all of the electricity that would have ordinarily gone through the grounding prong went out to the plug instead.

With all of those problems, I personally wouldn't plug anything into that socket the way it is right now. You may also have too many amps for the socket to handle. Check the size of the breakers or fuses at the box. Air conditioners pull a lot of amperage, compared to something like a house fan or coffee pot.

anon337576
Post 24

When I put up the plug of my Hitachi air conditioner into the three pin socket, I mean there were yellow sparks when the plug just touched the surface of the three pin socket. Now it's hot and I'm scared to switch on the air conditioner. wither the socket will catch fire, damage the circuit, damage the appliance or my electricity will shut down. I used a tester, and when I inserted the tester into the socket, there was no light on the tester. Does this mean that the socket is all right and I should go ahead and switch on the air conditioner or wait for the moron electrician who is not coming?

anon337388
Post 23

Can a fire start if there is a spark?

anon336211
Post 21

I recently had a ihome plugged into my outlet and it sparked and killed the power, so I waited 30 minutes and started recording on my phone to see what would happen after I got the breaker switched on. I came into the house to see what happened and it sparked again, but there are no black marks whatsoever.

Heligirl
Post 19

I just replaced the plug to the fan in my home. I used it in one room with no problem. I moved it to my bedroom and plugged it into a power strip. I did not have it turned on. About 30 seconds to 1 min. later there was a big flash and the breaker was tripped. There was a black mark on the cord just next to the plug. I thought that this must have been due to the power strip which was old. (I have had trouble with the power strips before.)

On another day, I plugged the fan into the wall with an extension cord, again I had the fan off, and about 30 seconds later there was a flash and pop about identical to the first. I am wondering what is wrong. Is it the outlet? Is it that I did not plug it into the wall directly? Did I do something wrong when I replaced the plug or is there something wrong with the fan itself? Help.

llhdc
Post 16

This was my question, posted several years ago. My husband and I own a carpet cleaning company. Our insurance company just paid out over $300,000 for a house fire which started in a floor outlet four days after we cleaned their carpet.

Outlets with shorts should switch off from a breaker, and when they don't it is clearly a problems with the outlet, regardless of whether water reaches the socket (which in this case did not happen from our carpet cleaning.)

This is just a cautionary tale to homeowners and business owners. Be careful -- you never know where the courts will place liability.

anon249081
Post 15

If a receptacle shorts out and turns black, do not use it. Same with loose fitting receptacles - if it feels loose when you plug something in, it should be replaced. Receptacles are not expensive and should be replaced when they aren't working properly. Better than burning down your home.

anon243240
Post 14

I recently plugged my cell phone charger into an outlet and almost immediately after I plugged in my cell phone, there was a big bang and the power went out. Now the outlet is all black. Can I still use the outlet or should I get it replaced? Also any ideas how a cell phone charger can cause such a short circuit?

anon154330
Post 13

one of my sockets just just sparked and popped but nothing was plugged in on the socket at all, so now it has a burned black mark on the outside. why would this happen and is it dangerous?

anon149187
Post 12

I've tried to plug a computer charger and a surge protector (with nothing attached to it) into my wall socket. The surge protector sparked at the socket and momentarily killed the power in the room but quickly came back on (enough to cause my modem to reboot).

But the charger plug sparks at the socket, then kills all power to the room,but the power goes back on when I pull out the plug. What's happening? What needs repair? Thanks! --David

Laz Cooper
Post 11

my power saw has just cut a power cable to a light outside in a garden.

anon136969
Post 10

For the record: Frequency (Hertz or cycles-per-second) his not the same as current (Amperage), and is a characteristic only relevant in AC circuits. Current at a given outlet is limited by the ampacity (or ability to carry Amperes) of the circuit "upstream" of it, to the wire, junctions, and circuit breaker.

anon125645
Post 9

I just want to ask why a wire has a copper wire covering. What is that for?

anon122151
Post 8

There are three 15 Amp outlets on one circuit. A large microwave is on one and the other two are for random appliance use.

One of the outlets started sparking when we used the microwave, and when I pulled out the outlet (after turning off the breaker of course) the plastic had melted around one of the screws for the white wire. Should I be using a different amp outlet other than 15 because the microwave pulling too much electricity? Or could it just be arching like you mentioned above? (The outlet is housed in a metal box.)

anon101381
Post 7

somehow, the plug to my computer has gotten damaged every time i plug it in to any outlet. probably because i started plugging it in a loose outlet, and that began happening.

i should probably replace the damaged plug, shouldn't i?

anon100228
Post 6

Important question: how can you tell the difference between a normal spark and when it might be something dangerous? What are the warning signs? Thanks!

anon95946
Post 5

I just pulled a light out to plug a fan in and it started sparking in the wall. what would it be that caused this because the above doesn't match.

anon89005
Post 4

The article is missing some vital information. If an appliance cord does not fit snugly into the receptacle, there is greater chance for arcing and a fire. This is especially true of appliances that draw a lot of power, such as one that has a heating element.

After use, if the plug feels unusually hot to the touch (not slightly warm), there is a problem that should be checked out.

llhdc
Post 3

Can a fire start in a floor receptacle from water sprayed (carpet cleaning) on or near the outlet?

Johnson
Post 2

Once there was a little blue spark when I plugged an external DVD burner into the socket. Can this damage the DVD burner, and more important: can this (e.g. the laser of the drive) damage any CD's or DVD's that I play in that same drive afterwards?

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