Triboluminescence isn't electric, it's chemical (well - physical really, but not electrical). It refers to a substance giving off light when subjected to mechanical stress. It's a lot more common than you'd think, but the light is so weak it's rarely noticed. As far as I know, all types of sticky tape do this to some extent. But we tend to notice those we tear in the darkroom.

I had a feeling I would be asked to explain this...