Discussion
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- Question
With increase in temperature, the electrical conductivity would
Options- A. increase in metals as well as in intrinsic semiconductor
- B. increase in metals but decrease in intrinsic semiconductor
- C. decrease in metals but increase in intrinsic semiconductor
- D. decrease in metals as well as in intrinsic semiconductor
- Correct Answer
- decrease in metals but increase in intrinsic semiconductor
ExplanationIncrease in temperature causes resistivity of metals to increase and resistivity of intrinsic semiconductors to decrease.Conductivity is reciprocal of resistivity.
Materials and Components problems
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- 1. Hall effect is observed in a specimen (metal or semi- conductor) when it is carrying current and is placed in a magnetic field. The resultant electric field inside the specimen is
Options- A. normal to both current and magnetic field
- B. in the same direction as current
- C. in a direction anti parallel to magnetic field
- D. none of the above Discuss
Correct Answer: normal to both current and magnetic field
- 2. The capacitance of a capacitor is not affected by
Options- A. area of plates
- B. thickness of plates
- C. ?r
- D. distance between plates Discuss
Correct Answer: thickness of plates
Explanation:
Capacitance depends on area, distance and ?r but not on thickness of plates.- 3. The charge per proton is
Options- A. 1.6 x 10-19 C
- B. 2.6 x 10-19 C
- C. 0.6 x 10-19 C
- D. 1.6 x 10-13 C Discuss
Correct Answer: 1.6 x 10-19 C
Explanation:
Because charge on proton is positive but numerically equal to that on electron.- 4. Assertion (A): If an atom of polarizability a is placed in homogeneous field E, the energy stored is 0.5 aE2.
Reason (R): Capacitance of an isolated conducting sphere R in vacuum is 4 p?0 R farads.
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
- 5. Schrodinger wave equation is partial differential equation.
Options- A. True
- B. False Discuss
Correct Answer: True
- 6. Yettrium-iron garnet (Y2Fe5O12) is a soft magnetic material suitable for applications involving
Options- A. dc
- B. 50 Hz ac
- C. ac of a few K Hz
- D. ac of a few hundred MHz Discuss
Correct Answer: dc
Explanation:
Yettrium iron garnet has very low eddy current loss. Hence it is used at frequencies in MHz range.- 7. For a diamagnetic material, ?r = 1.
Options- A. True
- B. False Discuss
Correct Answer: True
- 8. An electron for which l = 0 has zero orbital magnetic dipole moment.
Options- A. True
- B. False Discuss
Correct Answer: True
- 9. A magnetic field exists around
Options- A. moving charges
- B. static charges
- C. iron
- D. copper Discuss
Correct Answer: moving charges
- 10. The resistance of a photoconductor
Options- A. increases with increase in light intensity
- B. decreases with increase in light intensity
- C. may increase or decrease with increase in light intensity
- D. remains constant Discuss
Correct Answer: decreases with increase in light intensity
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