Materials and Components problems
- 1. The number of valence electrons in trivalent impurity is
Options- A. 5
- B. 4
- C. 3
- D. 1 Discuss
Correct Answer: 3
Explanation:
Trivalent means 3 valence electrons.
- 2. Assertion (A): In a conductor, current density remains constant in time as long as E is constant.
Reason (R): In a conductor, J = ?E.
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
Explanation:
In conductors constant E means constant current because conductivity is constant.
- 3. The most important primary force of attraction in the formation of solids is
Options- A. electromagnetic
- B. electrostatic
- C. quantum-electrostatic
- D. quantum electromagnetic Discuss
Correct Answer: electrostatic
- 4. The units of polarization of dielectric are
Options- A.
- B.
- C. Cm
- D.
Discuss
Correct Answer:
Explanation:
Polarization P = ?0(?r - 1)E.
Therefore units of Polarization = 
.
- 5. Antiferromagnetic materials do not have permanent dipoles.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
Anti-ferromagnetic materials have permanent dispoles but antiparallel orientation of equal moments.
- 6. Silicon and germanium are elements in the
Options- A. second column of periodic table
- B. third column of periodic table
- C. fourth column of periodic table
- D. fifth column of periodic table Discuss
Correct Answer: fourth column of periodic table
- 7. An atom of polarizability a is placed in a homogeneous electric field E. The energy stored in polarized atom is
Options- A. aE2
- B. a2E
- C. ½ aE2
- D. ½ aE Discuss
Correct Answer: ½ aE2
- 8. A capacitor can be represented by a capacitance and resistance in parallel. For a good capacitor, this parallel resistance should be
Options- A. negligible
- B. low
- C. high
- D. very high Discuss
Correct Answer: very high
Explanation:
The dielectric of a good capacitor should have very high resistivity.
- 9. When a potential is applied across an intrinsic semiconductor, holes flow
Options- A. towards positive terminal
- B. away from positive terminal
- C. in the external circuit only
- D. none of the above Discuss
Correct Answer: away from positive terminal
Explanation:
Holes are positively charged and move away from positive terminal.
- 10. ?0 has no other physical meaning than that of a fundamental conversion factor.
Options- A. True
- B. False Discuss
Correct Answer: True
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