In the interior of a metal in static equilibrium the charge density ρ is:
zero always.
never zero.
sometimes zero, sometime non-zero, depending on the conditions.
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Quiz 1 on Friday (CU-WIP folks Thursday)
Last 20 minutes of class
No cheat sheets; all formulas will be provided
Solve a Gauss' Law Problem with spherical symmetry
Sketch a graph of the resulting electric field
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Which of the following is a correct statement of charge conservation?
dQencdt=−∫J⋅dl
dQencdt=−∫J⋅dA
dQencdt=−∫∇⋅Jdτ
dQencdt=−∇⋅J
None of these or more than one of these
For everyday currents in home electronics and wires, which answer is the order of magnitude of the instantaneous speed of the electrons in the wire?
more than km/s
m/s
mm/s
μm/s
nm/s
An electric current I flows along a copper wire (low resistivity) into a resistor made of carbon (high resistivity) then back into another copper wire. In which material is the electric field largest?
In the copper wire
In the carbon resistor
It's the same in both copper and carbon
It depends on the sizes of the copper and carbon
Activity: A copper cylinder is machined to have the following shape. The ends are connected to a battery so that a current flows through the copper.
Rank order (from greatest to smallest, e.g. A=C>B)
Magnitude of E field, Conductivity, Current, & Current Density
Inside this resistor setup, (real world, finite sizes!) What does the E field look like inside ?
Must be uniform and horizontal
Must have some nonuniformity, due to fringing effects!
In the interior of a metal in static equilibrium the charge density ρ is:
zero always.
never zero.
sometimes zero, sometime non-zero, depending on the conditions.
Correct Answer: A