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- Question
The specific gravity of tungsten is 13.8 and its atomic weight is 184.0 Assume that there are two free elements per atom. Then the Fermi level or characteristic energy for the crystal in eV will be
Options- A. 8.95 eV
- B. -8.95 eV
- C. 7.326 eV
- D. -7.326 eV
- Correct Answer
- 7.326 eV
ExplanationA quantity of any substance equal to its molecular weight in grams is a mole of that substance contains the same number of molecules as one mole of any other substance. This Avogadro's number and equals 6.02 x 1023 molecules per mole. Thus
= 9.03 x 1028 electrons/m3
Since for tungsten the atomic and the molecular weights are the same. Therefore for tungsten
EF = 3.64 x 10-19(?)2/3
= 3.64 x 10- 19(9.03 x 1028)2/3
EF = 7.326 eV.
More questions
- 1. The maximum signal propagation time of a geosynchronous satellite transmission is about __________ millisecond.
Options- A. 540
- B. 270
- C. 135
- D. 1080 Discuss
Correct Answer: 270
- 2. In carbon resistor colour code, the third band is red. It indicates
Options- A. two zeros
- B. three zeros
- C. multiplier is 0.01
- D. multiplier is 0.1 Discuss
Correct Answer: two zeros
- 3. Low-orbit satellites are not used for communications because they
Options- A. produce sonic booms
- B. do not provide 24 hour/ day contact to the users on Earth
- C. heat up and melt
- D. none Discuss
Correct Answer: heat up and melt
- 4. When a thyristor is conducting, the voltage drop across it is about
Options- A. 1 V
- B. 10 V
- C. 100 V
- D. 0.1 V Discuss
Correct Answer: 1 V
- 5. In a TWT the phase velocity of the axial component of the field on the slow wave structure is kept
Options- A. equal to velocity of electron
- B. slightly less than velocity of electron
- C. slightly more than velocity of electron
- D. equal to velocity of light in free space Discuss
Correct Answer: equal to velocity of electron
- 6. Assertion (A): SUS is a PUT and avalanche diode connected between gate and cathode
Reason (R): SBS has two SUS inbuilt together and connected in anti-parallel
Options- A. Both A and R are correct and R is correct explanation of A
- B. Both A and R correct but R is not correct explanation of A
- C. A is correct but R is wrong
- D. A is wrong but R is correct Discuss
Correct Answer: Both A and R correct but R is not correct explanation of A
- 7. In a CRO which of the following is not a part of electron gun
Options- A. cathode
- B. grid
- C. accelerating anode
- D. X - Y plates Discuss
Correct Answer: X - Y plates
Explanation:
Electron gun consists of cathode, grid and accelerating anode.- 8. Which of the following can be accessed only sequentially?
Options- A. Floppy disk
- B. Hard disk
- C. Magnetic tape
- D. ROM Discuss
Correct Answer: Magnetic tape
Explanation:
Magnetic tape can be accessed only sequentially.- 9. Which of the following is not a valid variable name in C?
Options- A. p o, t
- B. p o t
- C. po_t
- D. p_ot Discuss
Correct Answer: p o, t
Explanation:
Comma is not allowed.- 10. A magnet does not attract
Options- A. nickel
- B. iron
- C. copper
- D. iron and copper Discuss
Correct Answer: copper
Explanation:
Only copper is non-magnetic.
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