Spring 2005
MWF 11:30
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.