6 worked answers · short steps first, explanations when you need them
Chapter 14 Exercises
Textbook pages 342
Question 1
Which statement is true for n-type silicon? (a) Electrons are majority carriers and trivalent atoms are dopants. (b) Electrons are minority carriers and pentavalent atoms are dopants. (c) Holes are minority carriers and pentavalent atoms are dopants. (d) Holes are majority carriers and trivalent atoms are dopants.
Steps only
Pentavalent dopants donate electrons, so electrons are the majority carriers and holes are the minority carriers.
Answer
(c).
Question 2
Which statement from Exercise 14.1 is true for p-type silicon?
Steps only
Trivalent dopants create holes, making holes the majority carriers.
Answer
Statement (d).
Question 3
Carbon, silicon, and germanium each have four valence electrons. Which ordering of their band gaps is correct? (a) Eg(Si)<Eg(Ge)<Eg(C); (b) Eg(C)<Eg(Ge)>Eg(Si); (c) Eg(C)>Eg(Si)>Eg(Ge); (d) all three gaps are equal.
Steps only
5.4 eV > 1.1 eV > 0.7 eV.
Answer
(c).
Question 4
In an unbiased p-n junction, holes diffuse from the p-region to the n-region because: (a) free electrons in the n-region attract them, (b) they move across due to the potential difference, (c) hole concentration is greater in the p-region than in the n-region, or (d) all of the above.
Steps only
Holes diffuse from higher to lower concentration, so they move from the hole-rich p-side to the n-side.
Answer
(c).
Question 5
What happens to the potential barrier when a p-n junction is forward biased? (a) It rises. (b) Majority-carrier current becomes zero. (c) It becomes lower. (d) None of these.
Steps only
Forward bias opposes the junction field and reduces the barrier.
Answer
(c).
Question 6
For a 50 Hz input, what is the output frequency of (a) a half-wave rectifier and (b) a full-wave rectifier?
Steps only
Half-wave: f_out=f_in=50 Hz. Full-wave: f_out=2f_in=100 Hz.