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- Question
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
- Correct Answer
- aT < ri
ExplanationAt very low temperatures a T ? 0. Since resistivity has a finite value even at low temperature, a T < ri.
More questions
- 1. Tesla is a unit of
Options- A. flux
- B. field strength
- C. flux density
- D. MMF Discuss
Correct Answer: flux density
- 2. In a receiver, which of the following device has IF input but RF output?
Options- A. Demodulator
- B. Loudspeaker
- C. Audio amplifier
- D. Frequency changer Discuss
Correct Answer: Demodulator
- 3. In Fermi-Dirac statistics, the probability of electron occupation of an energy level equal to Fermi level is
Options- A. 0
- B. 0.25
- C. 0.5
- D. 1 Discuss
Correct Answer: 0.5
- 4. In a shield helix
Options- A. the spacing between adjacent turns is very large
- B. the spacing between adjacent turns approaches zero
- C. the spacing between adjacent turns approaches zero and wire thickness approaches zero
- D. the spacing between adjacent turns is very large wire thickness approaches zero Discuss
Correct Answer: the spacing between adjacent turns approaches zero and wire thickness approaches zero
- 5. Match the following:
List I List II A. 200 MHz 1. SHF B. 20 GHz 2. UHF C. 500 kHz 3. VHF D. 500 MHz 4. MF
Options- A. A-3, B-1, C-4, D-2
- B. A-3, B-2, C-4, D-1
- C. A-3, B-4, C-1, D-2
- D. A-3, B-4, C-2, D-1 Discuss
Correct Answer: A-3, B-1, C-4, D-2
- 6. A line of characteristic impedance Z0 branches into two line each with characteristic impedance Z0. The refracted voltage is
Options- A. zero
- B. infinite
- C. equal to incident voltage
- D. two third of incident voltage Discuss
Correct Answer: two third of incident voltage
- 7. Iron has a body centred cubic structure.
Options- A. True
- B. False Discuss
Correct Answer: True
- 8. A surge voltage
Options- A. has very high magnitude and very long duration
- B. has very high magnitude and very small duration
- C. has very high magnitude and very small duration and can be positive or negative
- D. can be only positive Discuss
Correct Answer: has very high magnitude and very small duration and can be positive or negative
- 9. The Ohm's law for conduction in metals is
Options- A. J = ?E
- B. J =
- C. J ? ?E
- D. J ?
Discuss
Correct Answer: J = ?E
- 10. The following components are used to measure power output of a 2 kW TWT amplifier
- TWT
- Low pass/High pass filter
- Low power 20 dB attenuator
- 40 dB directional coupler with matched load
- Power meter.
Options- A. 1, 4, 2, 3, 5
- B. 1, 3, 4, 2, 5
- C. 1, 2, 4, 3, 5
- D. 1, 4, 3, 2, 5 Discuss
Correct Answer: 1, 3, 4, 2, 5
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