Instructor: Dr. Bruce Law, CW
327, Tel: 532-1618.
E22.30. By rubbing the balloon against your hair you have charged the balloon (say negatively). The balloon sticks to the door by electrical induction (i.e. the negatively charged balloon induces a separation in charge for atoms composing the door. The positively charge nucleus of the atoms is attracted to the balloon while the negative charged electrons of the atoms are repelled by the balloon. The attraction (between the balloon and the positively charge nucleus of the door atoms) is stronger than the repulsion (between the balloon and the negatively charged electrons of the door atoms) and therefore the balloon sticks to the door.
E22.31. A charged atom attracts a neutral atom by electrical induction. (See previous question for an explanation.)
PROBLEMS OF Home Work 19
P22.1. The force F is proportional to 1/d2 where d is the separation distance. If you increase d by a factor of 2 then you must decrease F by a factor of 4, i.e. the new force F = 20/4 = 5N.