When a balloon is rubbed against your hair or some fabric, it becomes electrically charged. This happens because electrons are transferred from one material to another, giving the balloon a net negative charge. Now, when you bring this charged balloon close to a wooden wall, an interesting phenomenon occurs.
Wood is typically an insulator, meaning it does not conduct electricity well, but it can still be slightly affected by electric charges. The balloon’s negative charge repels electrons in the wooden wall, causing a separation of charges within the wood. This process is known as polarization.
As a result, the side of the wall that is closest to the balloon becomes positively charged due to the deficiency of electrons, while the far side remains neutral or slightly negative. The attraction between the negatively charged balloon and the positively charged side of the wall creates enough of an adhesive force for the balloon to stick to it.
This sticking effect won’t work as well if you move the balloon too far away, as the distance between the charges weakens the attraction. The balloon will also eventually lose its charge over time or if it contacts other materials. But while it remains charged and close enough, it will continue to stick to the wooden wall due to these electric forces at play.