1.2 Charges can move from one place to another

Q1. Materials that has been charged by contact doesn't stay charged forever. For instance,your hair sticks to the balloon right afger you charge it by rubbing it to your hair. But after a while, you put the balloon on your head on nothing happens. Can you explain this?

A1. We can explain this by saying we are connected to the ground. The earth is so big that a few electrons moving into it or out of it won't change its charge visibly. So the charges formed will eventually, disappear into the earth. But objects hanging from a string lose charge, too. That's because air molecules bump into us. They are not as dependable as the solid ground, but with time they will take away your extra charge.

Q2. Imagine you are an electron inside a negatively charged ****l ball. One time, you are 1/5R away from the center. The second time, you find your self 1/3R away from the center. Compare the forces you feel.

A2. Inside ****ls, electrons are free to move. Inside, they feel forces from all directions. But the interesting thing is, where ever you are, the part covering you(the outer layer) exhibit forces that cancel  out with each other. So the electrons(the extra charge) move toward the outermost rim of the ball. And so, you probably wouldn't feel any force at all.