Materials and Components problems
- 1. A 200 turn coil has a self inductance of 10 mH. If the number of turns is doubled, all other quantities remaining the same, the self inductance will be
Options- A. 2.5 mH
- B. 5 mH
- C. 20 mH
- D. 40 mH Discuss
Correct Answer: 40 mH
Explanation:
Inductance is proportional to square of number of turns.
- 2. In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µr will
Options- A. increase
- B. decrease
- C. first decrease then increase
- D. first increase then decrease Discuss
Correct Answer: first increase then decrease
- 3. The number of valence electrons in acceptor impurity are
Options- A. 5
- B. 4
- C. 3
- D. 1 Discuss
Correct Answer: 3
- 4. Ferrites have
Options- A. a low copper loss
- B. low eddy current loss
- C. low resistivity
- D. higher specific gravity compared to iron Discuss
Correct Answer: low eddy current loss
Explanation:
Resistivity of ferrites is very high as compared to that of iron. Hence eddy curretns are much less.
- 5. A permeable substance is one
Options- A. which is strong magnet
- B. which is a weak magnet
- C. which is a good conductor
- D. through which magnetic lines of force can pass easily Discuss
Correct Answer: through which magnetic lines of force can pass easily
- 6. Which of the following is the poorest conductor of electricity?
Options- A. Aluminium
- B. Nichrome
- C. Copper
- D. All of the above Discuss
Correct Answer: Nichrome
- 7. In a pure sample of silicon
Options- A. the number of holes and free electrons is always equal
- B. the number of free electrons is more than the number of holes
- C. the number of free electrons and holes is equal at low temperature
- D. the number of free electrons is less than number of holes Discuss
Correct Answer: the number of holes and free electrons is always equal
- 8. In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.
Options- A. True
- B. False Discuss
Correct Answer: True
- 9. Assertion (A): In a parallel plate capacitor having area of plate 1 m2 and plate separation 1 m, the capacitance C and resistance R are given by C = ?0?'r and R =
where ? is frequency, ?r' and ?r" are real and imaginary parts of dielectric constant.Reason (R): The imaginary part of electric constant is responsible for dielectric losses.
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
- 10. Assertion (A): When an electron is revolving in its orbit and magnetic field is also present, the angular frequency of electron will be affected by the magnetic field.
Reason (R): In the case of electron revolving in its orbit in the presence of magnetic field, the orbital magnetic dipole moment is not affected by the presence of magnetic field.
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 true but R is false
Explanation:
Orbital magnetic moment is equal to (-e/2m).
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