To demonstrate Static Electrical Attraction.
Hold one end of a short piece of thread and your other hand, rub a pocket comb on your clothing. Then bring the comb near the free end of the thread. You will find you can make the thread stand upright as shown. If the comb is moved, the thread will also move in along with it. Static electricity makes the trick possible which is due to friction which causes free electrons to leave your clothing and attach themselves to the comb, giving it a negative electric charge. The thread behaves exactly like a simple electroscope. Free electrons are repelled from the thread, leaving it positively charged. As opposite charges attract, it is drawn towards the negatively charged comb. The experiment works best on cold dry days. This is because as water is an excellent conductor of electricity that, if the air is too humid there will be a rapid leakage of the electrical charge.