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CHAPTER 12
ELECTRICAL PROPERTIES
LEARNING OBJECTIVES
1.
Give two equation forms of Ohm's law.
2.
Given the electrical resistance, as well as length and cross-sectional area of a
specimen, compute its resistivity and conductivity.
3.
Compute the electric field intensity given the voltage drop across a specified
distance.
4.
Make the distinction between electronic and ionic conduction.
5.
Describe the formation of electron energy bands as a large number of atoms,
initially widely separated and isolated from one another, are gradually
brought together, and allowed to bond to one another such that a crystalline
solid is formed.
6.
Briefly describe the four possible electron band structures for solid materials.
7.
Briefly describe the electron excitation events that produce free
electrons/holes in metals, semiconductors (intrinsic and extrinsic), and
insulators.
8.
Calculate the mobility of an electron, given its drift velocity and the
magnitude of the electric field.
9.
Calculate the electrical conductivity of a metal, given the number of free
electrons per unit volume, the electron mobility, and the electrical charge on
an electron.
10. (a) Cite three sources of electron scattering centers for metals.
(b) Write Matthiessen's rule in equation form.
11. Calculate the temperature component of electrical resistivity for a metal at
some temperature, given values for the constants 0 and a.
12. For a solid solution alloy, given the impurity concentration (in atom fraction)
and a value for the constant A, calculate the impurity contribution to the
electrical resistivity.
13. For a two-phase metal alloy, determine the impurity contribution to the
electrical resistivity given volume fractions and electrical conductivity values
for the two phases.
14. (a) Briefly explain the nature and source of the safety problem that exists at
the connection point between aluminum and copper wires.
(b) Describe the best procedure for making these connections safe.
15. Distinguish between intrinsic and extrinsic semiconducting materials.
16. Cite two examples for each of the Groups IVA, IIIA-VA, and IIB-VIA
semiconducting materials.
17. Describe the formation of a hole in terms of electron excitations in
semiconductors.
18. Compute the electrical conductivity of an intrinsic semiconductor given the
electron and hole mobilities, the electronic charge, and the intrinsic carrier
concentration.
19. For n-type extrinsic semiconduction:
(a) Describe the excitation of a donor electron in terms of both electron
bonding and energy band models.
(b) Compute the electrical conductivity given the electron mobility, the
number of free electrons per unit volume, and the electronic charge.
20. For p-type extrinsic semiconduction:
(a) Describe the electron excitation that involves the formation of a hole in
terms of both electron bonding and energy band models.
(b) Compute the electrical conductivity given the hole mobility, the number
of holes per unit volume, and the electronic charge.
21. (a) On a plot of logarithm of carrier (electron, hole) concentration versus
absolute temperature draw schematic curves for both intrinsic and extrinsic
materials.
(b) On the extrinsic curve, note freeze-out, extrinsic, and intrinsic regions.
22. On a plot of logarithm of carrier mobility versus logarithm of impurity
concentration plot schematic curves for both electron and hole mobilities.
23. For an extrinsic semiconductor, given a plot of logarithm electron/hole
mobility versus logarithm of temperature (with curves at various dopant
levels), compute the conductivity at some dopant concentration and specified
temperature.
24. (a) Briefly describe the experimental setup that is used to demonstrate the
Hall effect.
(b) Note the primary reason that Hall effect measurements are made.
25. Compute the Hall constant, given the specimen thickness, and values for the
electric current, applied magnetic field, and the Hall voltage.
26. (a) For a p-n rectifying junction describe electron and hole distributions in
both forward and reverse biases.
(b) Now explain the process of rectification by means of electron and hole
motions in response to these two bias modes.
27. In terms current-voltage characteristics for both forward and reverse biases,
describe how a p-n junction acts as a rectifier.
28. For both junction and MOSFET transistors: (a) detail the configuration of
the various components, and (b) explain the operation for both transistor
types.
29. Compute the mobility of an ionic species given its valence and diffusion
coefficient, and, in addition, temperature, Boltzmann's constant, and the
electrical charge associated with an electron.
30. Compare electrical conductivity magnitudes for typical ceramics and
polymers with those of the metallic materials.
31. Define the following: (a) electric dipole, (b) dielectric material, and (c)
polarization.
32. Compute the capacitance given the applied voltage and magnitude of charge
stored on each plate.
33. Given plate area and plate separation for a parallel-plate capacitor, and, in
addition, the permittivity of a vacuum, calculate the capacitance.
34. Define dielectric constant in terms of permittivities.
35. Calculate the dipole moment for a single dipole given the magnitude of each
dipole charge and the charge separation distance.
36. Given the electric field and the permittivity for a material, determine the
dielectric displacement.
37. Briefly explain how the charge storing capacity of a capacitor may be
increased by the polarization of a dielectric material that has been inserted
between its plates.
38. Compute the polarization for a typical dielectric material given its
permittivity, as well as the permittivity of a vacuum and the applied electric
field.
39. Name and describe the three types of polarization.
40. Define and explain relaxation frequency as it applies to dielectric materials.
41. Define (a) dielectric breakdown, and (b) dielectric strength.
42. (a) Briefly describe the phenomenon of ferroelectricity.
(b) Explain ferroelectric behavior in barium titanate.
43. Briefly describe the piezoelectric phenomenon.