Materials and Components problems
- 1. The core of an atom consists of
Options- A. nucleus
- B. nucleus and all orbits
- C. nucleus and inner orbits
- D. none of the above Discuss
Correct Answer: nucleus and inner orbits
- 2. Diamagnetic materials do not have permanent magnetic dipoles.
Options- A. True
- B. False Discuss
Correct Answer: True
- 3. Assertion (A): Rochelle salt and Barium titanate are both ferroelectric.
Reason (R): Ferroelectric materials exhibit hysteresis effect.
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 but R is not correct explanation of A
Explanation:
Both the materials exhibit ferroelectric properties. Hysteresis effect is one of the features of ferroelectric materials.
- 4. If a metal specimen has n valence electrons per m3 each having charge e and mass m and t is the relaxations time, the conductivity is
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
- 5. Assertion (A): Intrinsic resistivity of silicon is lower than that of germanium.
Reason (R): Magnitude of free electron concentration in germanium is more than that of silicon.
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: A is false but R is true
- 6. In a conductor the current flow is due to
Options- A. holes
- B. electrons
- C. ions
- D. electrons and ions Discuss
Correct Answer: electrons
- 7. Assertion (A): The equation D = ?0?rE is applicable only to isotropic materials.
Reason (R): In polycrystalline materials, the directional effects are absent.
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 but R is not correct explanation of A
- 8. A dielectric of relative permittivity ?r is subjected to a homogeneous electric field E. The dipole moment P per unit volume is given by
Options- A. P = constant
- B. P = ?0 E
- C. P = ?0(?r - 1) E
- D. P = ?r E Discuss
Correct Answer: P = ?0(?r - 1) E
- 9. As per Matthiessen's rule, the total resistivity r of a conductor can be written as r = ri + aT, where ri and a are constants and T is absolute temperature. At very low temperatures
Options- A. aT = 0
- B. aT > ri
- C. aT ? ri
- D. aT < ri Discuss
Correct Answer: aT < ri
Explanation:
At very low temperatures a T ? 0. Since resistivity has a finite value even at low temperature, a T < ri.
- 10. Consider the following statements
- An iron cored choke is non linear and passive device.
- A carbon resistor kept in sunlight is a time invariant and passive device.
- A dry cell is a time varying and active device.
- An air capacitor is time invariant and passive device.
Options- A. 1, 2, 3 and 4 are correct
- B. 1, 2, 3 are correct
- C. 1, 2, 4 are correct
- D. 2 and 4 are correct Discuss
Correct Answer: 1, 2, 3 and 4 are correct
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