eli5: Why is there a tiny spark sometimes when plugging into an outlet?
In: Physics
If you live in a dry climate, you might see a blue or blue-white spark when you plug a plug into an outlet. That is static electricity that built up on you and your device as you moved around. Electric charge that built up on you (from you rubbing the carpet or whatever) jumps to the grounded (or close-to-grounded) wires in the outlet. As the charge jumps through the tiny air gap into the wire, it heats the air and makes it glow blue.
If you slowly plug in a high powered device (like a vacuum cleaner), and the device is switched on, you might see an orange or orange-white spark when you plug it in. That is little bits of the metal of the plug vaporizing from the high current draw through your device. In the moment you plug in the plug, electric current starts to flow. If you plug it in slowly, then for a tiny fraction of a second the electric current goes through a tiny contact patch at the front of the plug. If your device is drawing enough current, it heats or even vaporizes that little tiny bit of metal, making the orange spark.
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