Question

A balloon is negatively charged by rubbing and then clings to a wall. does this mean that the wall is positively charged? why or why not?

Answer 1

No. The wall is neutral but when you rub the balloon it gains electrons making it negative. When it goes near the wall the electrons in the wall repel so that the protons which are positive attract to the negative balloon. It falls because the wall will take electrons from the balloon.

Hope this helps!

Answer 2

When you rub the ballon, it steals electrons from the surface of the thing that is used to rub it.

Now, the electrons are un the surface of the ballon, and when you put it near the wall, the electrons of the wall are repelled by the large amount of electrons in the ballon, leaving only the positive charge in the surface of the wall, this positive surface is atracted by the ballon (and the ballon by the positive surface) and this is why the ballon clongs to the wall.