Why does electricity cause sparks?
Why does electricity cause sparks? I have two scenarios in my mind, and i hope someone can provide me good answers.
1) I have seen on a lot of occasions, for instance the main transformers near my home, the wires sometimes keep sparking near the area where the wires are joined to it. Why does it spark? What is actually happening? And i do know that it might be caused by an overload or a short-circuit or stuff, i am not talking about what caused the sparking, but what is happening when one occurs. Why not just burst into flames, or heat red hot like a metal filament or something?
2) I have also observed sparks when, lets say i suddenly pull out the plug from the socket with the switch still ON, or sometimes even when i turn ON/OFF a switch driving a load. Why does this occur?