The grains of puffed rice often stick to the inside of a foil bag. Similarly, if you rub a plastic tube with a silk cloth, small balls of light polystyrene will attach to its walls. You can also try to take off a silk scarf from a woollen coat. The scarf will hang almost horizontally in the air.

A school permanent magnet machine works on the similar principle. Two plastic discs with big nails rotate in opposite directions while flexible copper brushes pick up the electric charges created by rubbing. Additionally, the electric charges are stored in a kind of bottle with aluminium padding on the outside and inside.

All these phenomena are called electrostatics. The opposite charges created when you stand up wearing woollen trousers from a chair padded with synthetic fabric are so big that they could easily damage a portable laptop unless you discharge them on something else e.g. a radiator.

Electrifying through rubbing is a tribological phenomenon. It has nothing to do with tribes, though!

Rice seeds "stick" to the plastic walls thanks to the electrostatic interaction. Puffed rice seeds are light, small forces are sufficient to attract them.

But in general, the electrostatic potentials obtained by the friction (rubbing) are quite big. You risk sparks if you bring your finger 1 cm close to a water tap while taking-off a pure-wool pullover, especially with a nylon blouse underneath. This proves that voltages created are as high as 30,000 V.

Fortunately, the electrical charges are not big. If we compare the human body to a ball of 60 cm in diameter, the electrical capacity (C=R/k) would be only 6·10^-11 F, so with the voltage of 30 kV the electrical charges accumulated (Q = CV) wynosi zaledwie 18·10^-7 C. Energia wydzielona przy rozładowaniu palca wynosi ok. 54 mJ.