To make a roller rotate with the help of a balloon
1. An empty cylindrical soda can.
2. An inflated balloon.
Planning the Procedure
1. Place the can on a smooth horizontal table or floor and hold the can such that the can stays still.
2. Rub the balloon on your hair or take any woolen cloth and rub the balloon on it vigorously.
3. Next take the balloon and hold it about an inch away from the can. We will see the can will slowly start to roll.
4. Then make the balloon move by maintaining the distance and we will see that the can also starts to move along with the balloon.
5. If we bring the can to the other side we will see that the can will follow the balloon.
This is possible because of static charge. When we rub the balloon on our head the balloon gets charged with static electricity and polarizes opposite charge on the can. This develops a force of attraction as opposite charges attract and the can begins to follow the balloon as we move the balloon. We should try the same experiment to see if the can rolls uphill or not. We should also check how far the can rolls.
Principle of Xerox Machine: Even Xerox machine uses static electricity to make copies. In a Xerox machine there is a drum made of plastic. When we put a piece of paper that needs to be Xeroxed, a copy goes to the drum. There drum has static charge. This attracts the powdered black plastic powdered toner according to the dark areas of the paper. The toner melts and makes black letters on this new piece of paper. This is just like electrons (negatively charged) attract protons (positively charged).