Materials and Components problems
- 1. The chemical properties of atoms are determined by all the electrons and their configuration.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
Chemical properties are governed by valence electrons only.
- 2. If k is Boltzmann's constant and T is absolute temp, then at room temp.
Options- A. kT ≂ 0.025 eV
- B. kT ≂ 0.5 eV
- C. kT ≂ 1 eV
- D. kT ≂ 100 eV Discuss
Correct Answer: kT ≂ 0.025 eV
- 3. From a homogeneous and isotropic dielectric material of dielectric constant ?r, a small volume element is taken out creating a cavity. The field can be kept homogeneous if Di. (i.e., electric flux density inside the cavity) and D0 (i.e., electric flux density outside the cavity) are such that
Options- A. D0 = Di
- B.
- C.
- D. either (a) or (b) Discuss
Correct Answer:
Explanation:
Since the field is homogeneous 
.
.
- 4. At T = 0, the resistivity of a perfect single crystal of a metal is
Options- A. 0
- B. low
- C. high
- D. finite Discuss
Correct Answer: 0
Explanation:
At absolute zero temperature resistivity of metals is zero.
- 5. The iron core of a coil is removed so that it becomes an air cored coil. Its inductance will
Options- A. increase
- B. decrease
- C. remain the same
- D. may increase or decrease Discuss
Correct Answer: decrease
Explanation:
Because magnetic flux will decrease.
- 6. In a metal the probability of a state 0.1 eV below Fermi level being occupied
Options- A. is more than the probability of state 0.1 eV above Fermi level being occupied
- B. is the same as the probability of state 0.1 eV above Fermi level being occupied
- C. is less than the probability of state 0.1 eV above Fermi level being occupied
- D. may be equal to or more or less than the probability of state 0.1 eV above Fermi level being occupied Discuss
Correct Answer: is more than the probability of state 0.1 eV above Fermi level being occupied
- 7. When a ferromagnetic substance is magnetised there are small changes in dimensions. This phenomenon is called
Options- A. hysteresis
- B. magnetostriction
- C. diamagnetism
- D. dipolar relaxation Discuss
Correct Answer: magnetostriction
- 8. Electrical conductivity of metals expressed in ohm-1 m-1 is of the order of
Options- A. 1010
- B. 105
- C. 10-4
- D. 10-6 Discuss
Correct Answer: 105
Explanation:
Conductivity is reciprocal of resistivity. Since resistivity of metals is around 10-7 ohm-m, conductivity is about 107 ohm-1 m-1. So 105 is the nearest value.
- 9. In a polyatomic gas, the types of polarization which exist together are
Options- A. electronic and orientational
- B. electronic and ionic
- C. ionic and orientational
- D. electronic, orientational and ionic Discuss
Correct Answer: electronic, orientational and ionic
Explanation:
All the three types of polarization exist in polyatomic gases.
- 10. In elemental dielectrics, the orientation and ionic polarization are absent.
Options- A. True
- B. False Discuss
Correct Answer: True
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