Conceptual Questions Chap. 17

1. Conceptual Questions Chap. 17 Carbon is a moderate electrical conductor. Its resistivity is in between that of good conductors and good insulators (see Table 17.1). • Edison’s original light bulb contained a carbon filament. How should carbon be described electrically? • Why don’t 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 don’t the free electrons all go to the surface? • 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? • Use the atomic theory of matter to explain why the resistance of a material should increase as its temperature increases. 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.