Conceptual Questions Chap. 17

1
Conceptual Questions Chap. 17

1. Edisons original light bulb contained a carbon
   filament. How should carbon be described
   electrically?
2. Why dont the free electrons in a metal fall to
   the bottom of the metal due to gravity? Also,
   charges in a conductor are supposed to reside on
   the surface why dont the free electrons all go
   to the surface?
3. There is an old admonition given to experimenters
   to keep one hand in the pocket when working
   around high voltages. Why might this be a good
   idea?
4. Use the atomic theory of matter to explain why
   the resistance of a material should increase as
   its temperature increases.

Carbon is a moderate electrical conductor. Its
resistivity is in between that of good conductors
and good insulators (see Table 17.1).
The gravitational force acting on the electrons
is much weaker than the mutual electrical
repulsion force they experience, keeping the
electrons distributed throughout the metal. A
surface charge exists when there is an excess of
charge. Otherwise, the free electrons are simply
distributed throughout the conductor.
An electrical shock occurs when your body serves
as a conductor between two points having a
difference in potential. The concept behind the
admonition is to avoid touching points that are
at different potentials simultaneously.
The amplitude of atomic vibrations increases with
temperature, thereby scattering electrons more
efficiently.