Materials and Components problems
- 1. For a polyatomic gas, the equation relating dielectric constant ?r with molecular properties is
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
- 2. Assertion (A): For most metals, Fermi energy EF is less than 10 eV.
Reason (R): Fermi level of a metal is given by EF = 3.64 x 10-19 (n)2/3 where n is number of free electrons/m3 of metal.
Options- A. Both A and R are true and R is correct explanation of A
- B. Both A and R are true but R is not correct explanation of A
- C. A is true but R is false
- D. A is false but R is true Discuss
Correct Answer: Both A and R are true and R is correct explanation of A
- 3. The relaxation time of electrons in a metal is of the order of
Options- A. 10-6 secs
- B. 10-10 secs
- C. 10-14 secs
- D. 10-20 secs Discuss
Correct Answer: 10-14 secs
- 4. As regards ?0 and ?r (absolute and relative permittivity)
Options- A. both ?0 and ?r can be interpreted in terms of atomic properties of medium
- B. only ?r can be interpreted in terms of atomic properties of medium
- C. only ?0 can be interpreted in terms of atomic properties
- D. ?r has no physical significance Discuss
Correct Answer: only ?r can be interpreted in terms of atomic properties of medium
- 5. An electron is moving in a circular orbit of radius R at angular velocity ?0 in a field free space. If a magnetic field B is created, the velocity of electron ? will be given by the equation
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
- 6. Even at room temperature, an intrinsic semiconductor has some holes. These holes are due to
Options- A. electron
- B. doping
- C. thermal energy
- D. free electrons Discuss
Correct Answer: thermal energy
- 7. At a very low temperature, a semiconductor
Options- A. becomes a conductor
- B. becomes an insulator
- C. may become a conductor or an insulator
- D. will remain a semiconductor becomes a conductor or an insulator Discuss
Correct Answer: becomes an insulator
Explanation:
Semi conductor becomes insulator at very low temperature.
- 8. Assertion (A): Helium, Argon and Neon are gaseous at room temperature.
Reason (R): The atoms in Helium, Argon and Neon are chemically extremely inactive.
Options- A. Both A and R are true and R is correct explanation of A
- B. Both A and R are true but R is not correct explanation of A
- C. A is true but R is false
- D. A is false but R is true Discuss
Correct Answer: Both A and R are true and R is correct explanation of A
- 9. The colour code on a carbon resistor is green-blue-yellow. The tolerance is
Options- A. ± 5%
- B. ± 10%
- C. ± 20%
- D. ± 30% Discuss
Correct Answer: ± 30%
- 10. The transition of electron from energy level W1 to W2 is associated with emission or absorption of electro magnetic radiation of frequency f such that
Options- A. hf = |W1 - W2|
- B. |W1 - W2|f = h
- C. hf = 0.5|W1 - W2|
- D. (hf)2 = |W1 - W2| Discuss
Correct Answer: hf = |W1 - W2|
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