Answer to Question #61585 in Electricity and Magnetism for hamid

Question

if we charge a balloon negatively, it cling to the wall. does it mean that the wall become +vely charge? and why it falls after sometime?

Answer 1

No the balloon doesn't cling to the wall because the wall is positively charged. The wall is neutral. This happens because the negative charge on the balloon will force some of the electrons in the wall to move to the other side of their atoms. This leaves the surface of the wall closest to the balloon positively charged. The positive surface of the wall and the negative surface of the balloon will attract each other. If the air is very dry, the balloon should stick for many hours. The moisture in the air can steal charges from the balloon, so on humid days this may not work at all. It falls because the wall will take electrons from the balloon.