Why does my Mac power adapter spark?

August 17, 2008 6:55 PM

When I plug my MacBook Pro Power Adapter into most/all outlets, I see a blue spark as the prongs enter the outlet. Is this normal?

I see and hear a spark every time I plug my MacBook Pro power adapter into an outlet. I'm using the standard two prong charger seen here. I think the sparking is a new thing. I don't remember this happening regularly before; I bought my MacBook pro two years ago. What causes the spark? Should I be worried about my charger (and ultimately, my laptop)? Does anyone else have this happening with their power adapters?

As a precaution, I make sure to plug the adapter into the wall before I connect it to my laptop.

For reference, the spark seems bigger than a standard static electricity spark.

posted by plasticbugs to computers & internet (10 answers total)

This is normal, but shouldn't be specific to what you're plugging in to the wall really. As the metal of the plug and the connector comes closer and closer there's a point where the air gap between the two points is no longer insulating enough to prevent the flow of electrons. At that point they jump the gap and ionize the air between the space and cause the glow you saw.

This is one of the reasons that if you suspect a gas leak you're not supposed to use anything electrical, even something as simple as a phone switch releasing will involve this air gap and a momentary spark.
posted by odinsdream at 7:08 PM on August 17, 2008

I have a Lenovo laptop with a 3-prong charger and it does the same thing. Nearly 8 months and I have never noticed any problems with the equipment. My cable is in 2 parts, so I plug the prongs into the wall, and then plug that cord into the adapter, and then connect the laptop. This seems to fix/lessen the problem. Did your charger come with a 3-prong adapter like this?
posted by PixelatorOfTime at 7:37 PM on August 17, 2008

Did your charger come with a 3-prong adapter like this?

Yep, it did but I don't use it very often because it's bulky and more to carry. I know it's safer electrically to be grounded, but I have Applecare - so I'm not as cautious as I ought to be.
posted by plasticbugs at 7:58 PM on August 17, 2008

My dell 2/3 prong adapters do the same thing, as does pretty much everything else I plug into the outlet. No fires yet.
posted by SirStan at 8:23 PM on August 17, 2008

My old iBook adapter did this a lot more than my newer MacBook adapter does, but yeah, I do see the arcing a lot more than with adapters for other devices I have.
posted by brownpau at 9:06 PM on August 17, 2008

This is totally normal, and isn't doing anything bad to your electronics or outlets or anything.

It probably won't happen if you plug in the power brick first and then the macbook second
posted by aubilenon at 9:26 PM on August 17, 2008

My MacBook AC adapter does this with the ungrounded 2-prong plug. I always try to plug the AC adapter into the outlet before I connect the other end to my MacBook, but I'm not sure that it would do any harm otherwise.
posted by Third at 9:56 PM on August 17, 2008

I have a Euro-spec MacBook, with the two round "male" plugs and one "female" hole. I see the spark all the time, but I noticed that if the adapter is plugged into the MacBook first and then the wall, it hardly ever happens.
posted by DefendBrooklyn at 5:13 AM on August 18, 2008

Like most power supplies, your laptop power adapter includes a large-ish capacitor in its input circuitry. When the adapter is plugged in there is a momentary inrush surge as that capacitor is charged up. It's normal; don't worry about it.
posted by ryanrs at 11:09 AM on August 18, 2008

ryanrs is exactly right. The spark is not ideal, since the electrical noise it radiates can upset some equipment. If you're plugging into a switched outlet, turn the outlet switch off until you've finished plugging in. You'll still cause a little spark inside the switch when you turn it on, but it will be much much shorter and won't radiate as much hash.
posted by flabdablet at 4:31 AM on August 19, 2008