Explain how a balloon can become positively charged when rubbed with a cloth

When you rub a balloon against your clothes and it sticks to the wall, you are adding a surplus of electrons (negative charges) to the surface of the balloon. The wall is now more positively charged than the balloon. As the two come in contact, the balloon will stick because of the rule that opposites attract (positive to negative).

For more static electricity information and experiments, see the list of Web Resources and Further Reading sections.