Why Does an Electrical Spark Occur?

[namannitant]

When a switch is in on condition say our home 230 volt ac switch,, and I plug in any electrical device in that on switch, there is spark , what is the reason of this spark..

please explain

 

[tiny-tim]

Welcome to PF!

Hi namannitant! Welcome to PF!

Air is a good insulator, but it's not perfect …

if the voltage per distance (in other words, the electric field, E) is high enough, then air will conduct …

when you move the plug closer to the socket, the voltage stays the same, so the voltage per distance gets higher, and when it's high enough, the air conducts, and that's the spark.

 

[sophiecentaur]

You will usually get a much bigger spark when you unplug a device (particularly a motor or something with large 'wound components'). This is because of the inductance which induces a high voltage, briefly, as the current reduces quickly. These sparks are a real nuisance as they can produce erosion of switch contacts and can be reduced using capacitors or diodes (in DC circuits).
namannitant. When you get your sparks from a plug it may well be because you start by making a brief contact and then break it.