Use the band theory of semiconductors to choose the most correct ...

[Jipu 123]

Use the band theory of semiconductors to choose the most correct statement below.
  a. A semiconductor primarily differs from an insulator in size of band gap.
  b.Materials that are generally called conductors contain an overlap in the conduction and valence bands.
  c. Conductors and semimetals are similar in band structure because of large band gaps.
  d. Electrons in insulators at room temperature can easily cross the band gaps.
  e. Semimetal materials are arranged structurally like metals but act as insulators because they have large band gaps.

Question 2

Which of the following is a property of a Josephson junction?
 

a. When no external magnetic or electric fields are applied, a small AC current is established across the junction.
  b. When an external oscillating voltage is applied across the junction, the current resonates in proportion to the oscillations.
  c. When an external DC voltage is applied, the current oscillates proportionally to that voltage.
  d. The zero resistivity property of the junction can be turned on and off with an applied AC current.

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Answer to Question 1

a.
The size of the band gap is what defines a semiconductor and insulator. Insulators generally have gaps as large as several electron volts, usually preventing electrons from being excited into the conduction band at normal temperatures. Semiconductors have smaller band gaps, allowing electrons to be excited thermally and a small current to be established under an electric potential

Answer to Question 2

c.
When an external DC voltage is applied across the junction, the current oscillates proportionally to the voltage. This is useful in determining to a high degree of accuracy the voltage of a given source.