Nib asked, and Nib — askNib's tutor — drew the answer live at a whiteboard. This is the spoken transcript; enable JavaScript to watch it drawn.
why does friction cause static electricity
Rub a balloon on your hair and it sticks to the wall. Everyone says friction made the charge. But rubbing is not the real secret. Contact is.
Charge is never made, only moved. Plain touching can shift some electrons across the contact. Rubbing helps only because it brings far more surface into touch.
At the contact, electrons hop. Rubber holds electrons more tightly than hair does, so electrons cross from the hair to the balloon.
Pull them apart. Hair and rubber are insulators, so the electrons cannot flow back. The balloon is left negative, the hair positive, equal and opposite.
And the wall? The balloon's extra electrons push the wall's electrons slightly away, leaving its near surface positive, and the closer pull wins. It sticks.
Rubbing doesn't make charge, it moves it: millions of tiny contacts shuffle electrons, and an insulator holds them in place.