Questions and answers for exam Preparation

MCQs

Total Questions : 47 | Page 4 of 5 pages

Question 31. An electron is moving with a velocity of 0.85c in the same direction as that of a moving photon.
The relative velocity of the electron with respect to photon is

c
-c
0.15c
-0.15c

Discuss Question

Answer: Option B. -> -c

-NA-

Question 32. Across a first order phase transition, the free energy is

proportional to the temperature
a discontinuous function of the temperature
a continuous function of the temperature but its first derivative is discontinuous
such that the first derivative with respect to temperature is continuous

Discuss Question

Answer: Option B. -> a discontinuous function of the temperature

-NA-

Question 33. If Planck's constant were zero, then the total energy contained in a box filled with radiation of all
frequencies at temperature T would be ( k is the Boltzmann constant and T is nonzero)

Zero
Infinite
3/2 k T
k T

Discuss Question

Answer: Option B. -> Infinite

-NA-

Question 34. An n-channel junction field effect transistor has 5mA source to drain current at shorted gate (IDSS) and 5V pinch off voltage (VP). Calculate the drain current in mA for a gate-source voltage (VGS) of -2.5V. The answer should be up to two decimal places. ________________

1.25
1.75
1.55
1.35

Discuss Question

Answer: Option A. -> 1.25

-NA-

Question 35. There are four energy levels E, 2E, 3E and 4E (where E >0). The canonical partition function of two particles is , if these particles are two distinguishable particles

e-2 Î² E + e-4 Î² E + e-6 Î² E + e-8 Î² E
e-3 Î² E + e-4 Î² E + e-5 Î² E + e-6 Î² E + e-7 Î² E
(e-Î² E + e-2 Î² E + e-3 Î² E)2
e-2 Î² E - e-4 Î² E + e-6 Î² E - e-8 Î² E

Discuss Question

Answer: Option C. -> (e-Î² E + e-2 Î² E + e-3 Î² E)2

-NA-

Question 36. There are four energy levels E, 2E, 3E and 4E (where E >0). The canonical partition function of two particles is , if these particles are two identical fermions

e-2 Î² E + e-4 Î² E + e-6 Î² E + e-8 Î² E
e-3 Î² E + e-4 Î² E + e-5 Î² E + e-6 Î² E + e-7 Î² E
(e-Î² E + e-2 Î² E + e-3 Î² E)2
e-2 Î² E - e-4 Î² E + e-6 Î² E - e-8 Î² E

Discuss Question

Answer: Option B. -> e-3 Î² E + e-4 Î² E + e-5 Î² E + e-6 Î² E + e-7 Î² E

-NA-

Question 37. A firm is selling its product at Rs. 60 per unit. The total cost of production is Rs. 100 and firm is
earning total profit of Rs. 500. Later, the total cost increased by 30%. By what percentage the price
should be increased to maintained the same profit level.

Discuss Question

Answer: Option A. -> 5

-NA-

Question 38. Abhishek is elder to Savar. Savar is younger to Anshul. Which of the given conclusions is logically valid and is inferred from the above statements?

Abhishek is elder to Anshul
Anshul is elder to Abhishek
Abhishek and Anshul are of the same age
No conclusion follows

Discuss Question

Answer: Option D. -> No conclusion follows

-NA-

Question 39. The entropy function of a system is given by S(E) = a E(E0 - E) where a and E0 are positive
constants. The temperature of the system is

negative for some energies
increases monotonically with energy
decreases monotonically with energy
Zero

Discuss Question

Answer: Option A. -> negative for some energies

-NA-

Question 40. Consider a linear collection of N independent spin 1/2 particles, each at a fixed location. The
entropy of this system is (k is the Boltzmann constant)