Solid State Physics - Study Mode
[#1] In simple metals the phonon contribution to the electrical resistivity at temperature T is
Correct Answer
(A) directly proportional to T above Debye temperature and to T 3 below it
Explanation
Solution: In simple metals , the phonon contribution to the electrical resistivity at temperature T follows specific trends based on the Debye temperature: Option A: This option is correct. Above the Debye temperature, the phonon contribution to the electrical resistivity is directly proportional to T. Below the Debye temperature, it is proportional to T 3 . This behavior is in accordance with the Debye theory of solids, which predicts these dependencies. Option B: This option is incorrect. The phonon contribution to electrical resistivity is not inversely proportional to T for all temperatures in simple metals. Option C: This option is incorrect. The phonon contribution to electrical resistivity is not independent of temperature for all temperatures in simple metals. Option D: This option is incorrect. While it states a direct proportionality above the Debye temperature, it incorrectly suggests a proportionality to T 5 below the Debye temperature. The correct dependency below the Debye temperature is T 3 , not T 5 . Therefore, this option is not accurate.
[#2] The effective mass of an electron in a semiconductor
Correct Answer
(C) can be positive or negative
[#3] Which one of the following is not correct statement about semiconductors?
Correct Answer
(C) Silicon is a direct band gap semiconductor
[#4] The effective mass of an electron in a semiconductor can be
Correct Answer
(D) negative near the top of the band
[#5] A solid superconductor is placed in an external magnetic field and then cooled below its critical temperature. The superconductor
Correct Answer
(D) expels out its magnetic flux because the surface current induces a field in the direction opposite to the applied magnetic field