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I plugged in the charger of my laptop into a socket, which I have done a lot of times but this time, I noticed a strange thing. When the contact was made between the pins of charger and the socket, there were sparks at both pins but one of them was orange and the had a blue shade. What causes the colors and why are they different for both the pins.

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  • $\begingroup$ "there were sparks at both pins but one of them was orange and the (other) had a blue shade". Can this observation be repeated in another turn of the experiment, or is it a one-time fluke? (Not that I would want to encourage you to repeat the sparking again and again, which could damage your charger, and/or hurt you! But this is natural curiosity.) $\endgroup$ – 299792458 Apr 29 '15 at 8:38
  • $\begingroup$ Also, related : Why does it spark when I push a plug in the electrical socket. This answers why there are sparks, why sparks are colored is also trivial ($\lambda$ pertaining to ionization of specific molecules/atoms). But this question is not a duplicate, because the main issue over here is - why are those two colors different? $\endgroup$ – 299792458 Apr 29 '15 at 8:42
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An electrical spark will vapourise part of the surface where it is generated. With a large spark this can cause visible pitting, though if the spark is small you may only be able to see the damage under a microscope.

Anyhow, just as in a flame metal ions present in the vapour can be excited by collisions and then decay to emit light. The colour of the light emitted will depend on what atoms are present in the flame and at what concentrations.

The trouble is I can't make any further comment because I can't inspect your plug and socket to see what might be causing the difference. I'd be surprised if the pins on the plug were made of different metals, but they might be corroded to a different extent and it could be metal atoms from the corrosion that are responsible. Alternatively it could be that different levels of corrosion mean the sparks are bigger and hotter on one pin than the other. Finally, the difference could be due to the contacts in the wall socket rather than on the plug.

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    $\begingroup$ Well following up on your explanation, it would be plausible that one of the sparks came from the copper plating inside the plug, while the other came from the plugger. As the plugger is made of some different alloy, different materials are vaporized on each side. The spark moves from one potential to another so the two sparks come from two different materials. $\endgroup$ – WalyKu Apr 29 '15 at 10:19
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    $\begingroup$ @Kurtovic: yes, good call, it could well be the case that the plug and socket are different metals (or different alloys) and that one spark vapourised more of the pin on the plug while the other spark vapourised more of the contact in the socket. $\endgroup$ – John Rennie Apr 29 '15 at 10:45

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