2. It may seem dangerous to be in a car during a
thunderstorm, but it's actually relatively safe. Since the car is essentially a metal box,
the inside of the car is electrically neutral. Why does any charge on the car
move to its outside surface?
The metal body of the car is a good conductor, which means that any charges
on the metal are relatively free to move. If another charge of the same type
happened to be nearby, each one would feel a repulsive force that increases
as they get closer together. These charges would move as far away from each
other as possible since they are free to move. Any charge of this type that
is on the inside surface of the metal body will try to move around to the far
side of the car on the outside surface, since that is the farthest away.
8. Suppose that you had an electrically charged stick. If you
divided the stick in half, each half would have half the original charge. If you split
each of these halves, each piece would have a quarter of the original charge. Can
you keep on dividing the charge in this manner forever? If not, why
not?
If there was no "minimum size" to electric charge, you would be able to
continue dividing the pieces in half forever. But we know about atoms
and the particles that seem to make them up: protons, electrons, and
neutrons. Protons have one unit of positive charge and electrons have
one unit of negative charge. We would not be able to subdivide the
pieces of our stick any further than their atomic limit.
10. If the forces between electric charges didn't diminish with
distance, an electrically charged balloon wouldn't cling to an electrically neutral
wall. Why not?
An electrically charged balloon clings to a neutral wall by polarizing the
molecules in the wall and inducing a separation of charges, with charge of
opposite polarity located nearest to the balloon on the wall and the remaining
complement of charge on the neutral wall farther away. Since the force between
charges decreases with distance, the attraction between neighboring, opposite
charges attracts the balloon to the wall. The repulsion between like charges is
smaller in size since they are farther away from the balloon. But if the force
did not decrease with distance, then this repulsion would be exactly the same
magnitude as the attraction to the nearby induced charge. Then the balloon would
experience equal and opposite forces, giving no net attractive force toward the
wall.
14. You're holding two oppositely charged balloons in your
hands. You begin to separate them. You do work on the balloons, so your energy
decreases. Where does your energy go?
You did work on the balloons, so the energy you expended is associated with
them. It did not become kinetic energy in this case, but you have increased
their electrostatic potential energy with respect to each other.
16. A bowling ball contains an enormous number of
electrically charged particles. Why don't two bowling balls normally exert electrostatic
forces on each other?
The electrically charged particles within each bowling ball do exert
electrostatic forces on each other at an atomic level. However, the
net electric charge that we see on a macroscopic scale is right around
zero. So, the two bowling balls do not exert electrostatic forces on
each other because they each have zero net charge overall.
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