MCQOPTIONS
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MCQOPTIONS
This section includes 27 Mcqs, each offering curated multiple-choice questions to sharpen your Electronic Devices Circuits knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A sample of Si is doped with 1017 donor atoms/cm3. Considering electron mobility in the doped Si 700 cm2/V-sec, the approximate resistivity of the doped Si is |
| A. | 1 Ω-cm |
| B. | 10 Ω-cm |
| C. | 0.1 Ω-cm |
| D. | 100 Ω-cm |
| Answer» D. 100 Ω-cm | |
| 2. |
According to Einstein’s relationship for a semiconductor, the ratio of the diffusion constant to the mobility of the charge carriers is |
| A. | Variable and is twice the volt equivalent of the temperature |
| B. | Constant and is equal to the volt equivalent of the temperature |
| C. | Equal to two and is twice the volt equivalent of the temperature |
| D. | Equal to one and is equal to the volt equivalent of the temperature. |
| Answer» C. Equal to two and is twice the volt equivalent of the temperature | |
| 3. |
A thin P-type silicon sample is uniformly illuminated with light which generates excess carriers. The recombination rate is directly proportional to |
| A. | the minority carrier mobility |
| B. | the minority carrier recombination lifetime |
| C. | the majority carrier concentration |
| D. | the excess minority carrier concentration |
| Answer» E. | |
| 4. |
Pure Metals generally have |
| A. | High Conductivity & Low temperature coefficient |
| B. | High Conductivity & High temperature coefficient |
| C. | Low conductivity & zero temperature coefficient |
| D. | Low Conductivity & High temperature coefficient |
| Answer» C. Low conductivity & zero temperature coefficient | |
| 5. |
A bar of silicon is doped with a boron concentration of 1016 cm-3 and assumed to be fully ionized. It is exposed to light such that electron-hole pairs are generated throughout the volume of the bar at the rate of 1020 cm-3s-1. If the recombination lifetime is 100 μs, the intrinsic carrier concentration of silicon is 1010 cm-3 and assuming 100% ionization of boron, then the approximate product of steady-state electron and hole concentrations due to this light exposure is |
| A. | 1032 cm-6 |
| B. | 1020 cm-6 |
| C. | 2 × 1032 cm-6 |
| D. | 2 × 1020 cm-6 |
| Answer» D. 2 × 1020 cm-6 | |
| 6. |
For an n-type Ge specimen, width = 4 mm, length = 1 mm, current (along the length of specimen) = 1 mA, magnetic field (perpendicular to the current flow direction) = 0.1 Wb/m2 and Hall voltage magnitude = 0.005 V. Calculate the majority carriers density. |
| A. | 3 × 1019 cm-3 |
| B. | 3 × 1019 m-3 |
| C. | 6 × 1019 cm-3 |
| D. | 6 × 1019 m-3 |
| Answer» C. 6 × 1019 cm-3 | |
| 7. |
If σ is the conductivity, What is the relation between the electric field E and the current density J in a conducting medium? |
| A. | σ = J/E |
| B. | σ = 1/JE |
| C. | σ = E/J |
| D. | σ = EJ |
| Answer» B. σ = 1/JE | |
| 8. |
For which one of the following materials, is the Hall coefficient closest to zero? |
| A. | Metal |
| B. | Insulator |
| C. | Intrinsic semiconductor |
| D. | Alloy |
| Answer» B. Insulator | |
| 9. |
On applying an electric field of intensity 10 V/cm across a semiconductor at a certain temperature the average drift velocity of free electrons is measured to be 70 m/s. Then the electron mobility is |
| A. | 7 × 104 cm2/Vs |
| B. | 700 cm2/Vs |
| C. | 7 cm2/Vs |
| D. | 700 cm/Vs |
| Answer» C. 7 cm2/Vs | |
| 10. |
Hall effect can be used to measure |
| A. | electric field intensity |
| B. | magnetic field intensity |
| C. | carrier concentration |
| D. | none of these |
| Answer» D. none of these | |
| 11. |
In the figure, \(\rm \ln{(r_i)}\) is plotted as a function of \(\rm 1/T\), where \(\rm r_i\) is the intrinsic resistivity of silicon, \(\rm T\) is the temperature, and the plot is almost linearThe slope of the line can be used to estimate |
| A. | Band gap energy of silicon Eg |
| B. | sum of electron and hole mobility in silicon μn + μp |
| C. | reciprocal of the sum of electron and hole mobility in silicon (μn + μp)-1 |
| D. | intrinsic carrier concentration of silicon \(\rm (n _i)\) |
| Answer» B. sum of electron and hole mobility in silicon μn + μp | |
| 12. |
Consider a semiconductor carrying current and placed in a transverse magnetic field B, as shown above. The measured potential across 1 and 2 surfaces is positive at 2. What is the type of material? |
| A. | Intrinsic Si material |
| B. | n-type semiconductor material |
| C. | p-type semiconductor material |
| D. | No such conclusion can be drawn |
| Answer» C. p-type semiconductor material | |
| 13. |
Directions: The below item consists of two statements, one labelled as the 'Statement (I)' and the other as 'Statement (II)'. Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I): Hall voltage is given by \({V_H} = {R_H}\frac{{I.H}}{t}\) where I is current, H is the magnetic field strength, t is the thickness of probe and RH is the Hall constant.Statement (II): Hall effect does not sense the carrier concentration.Codes: |
| A. | Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I) |
| B. | Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I) |
| C. | Statement (I) is true but Statement (II) is false |
| D. | Statement (I) is false but Statement (II) is true |
| Answer» D. Statement (I) is false but Statement (II) is true | |
| 14. |
Best Conductor of heat and electricity is |
| A. | Chromium |
| B. | Nickle |
| C. | Copper |
| D. | Aluminium |
| Answer» D. Aluminium | |
| 15. |
For a particular material, the Hall coefficient is found to be zero. The material is |
| A. | intrinsic semiconductor |
| B. | extrinsic semiconductor |
| C. | metal |
| D. | insulator |
| Answer» E. | |
| 16. |
Measurement of Hall coefficient enables the determination of: |
| A. | Temperature coefficient and thermal conductivity |
| B. | Mobility and concentration of charge carriers |
| C. | Fermi level and forbidden energy gap |
| D. | None of the above |
| Answer» C. Fermi level and forbidden energy gap | |
| 17. |
Hall effect is useful for the measurement of a semiconductor’s |
| A. | mobility, carrier concentration and temperature |
| B. | type (n-type or p-type), conductivity and temperature |
| C. | type (n-type or p-type), mobility and carrier concentration |
| D. | mobility, conductivity and temperature |
| Answer» D. mobility, conductivity and temperature | |
| 18. |
Given that at room temperature, the volt equivalent of temperature VT = 26 mV, hole mobility μp = 500 cm2/Vs and the lifetime of holes 130 ns, in a sample of n-type silicon bar that is exposed to radiation at one end at low-injection level, what is the diffusion length of holes? |
| A. | 1300 microns |
| B. | 100 Armstrongs |
| C. | 1699 microns |
| D. | 100 microns |
| Answer» B. 100 Armstrongs | |
| 19. |
A Hall-effect element is used for the measurement of magnetic field of 0.8 Wb/m2. The thickness of the element is 2.5 mm and is of bismuth material. If the current passed through the element is 4A, then the Hall emf developed will be: (Hall coefficient is 5 × 10-7) |
| A. | 1.4 × 10-4 V |
| B. | 6.4 × 10-4 V |
| C. | 2 × 10-7 V |
| D. | 3.2 × 10-4 V |
| Answer» C. 2 × 10-7 V | |
| 20. |
Electron mobility of the following intrinsic elements in descending order is |
| A. | GaAs, Ge, Si |
| B. | GaAs, Si, Ge |
| C. | Si, Ge, GaAs |
| D. | Ge, Si, GaAs |
| Answer» C. Si, Ge, GaAs | |
| 21. |
A semiconductor bar having a length of 4 cm is subjected to a voltage of 8 Volts. If the average drift velocity is 104 cm/s, then electron mobility would be: |
| A. | 4396 cm2/V-s |
| B. | 3 × 104 cm2/V-s |
| C. | 6 × 104 cm2/V-s |
| D. | 52 cm2/V-s |
| Answer» E. | |
| 22. |
In a semiconductor, Drift current is due to: |
| A. | volume gradient |
| B. | diffusion of charge |
| C. | concentration gradient |
| D. | applied electric field |
| Answer» E. | |
| 23. |
Drift velocity in metal is |
| A. | inversely proportional to the force on an electron due to applied electric field |
| B. | directly proportional to the mass of an electron |
| C. | proportional to the mobility of an electron |
| D. | inversely proportional to the strength of the applied electric field |
| Answer» D. inversely proportional to the strength of the applied electric field | |
| 24. |
If the drift velocity of holes under a field gradient of 200 V/m is 100 m/s, their mobility is SI units is |
| A. | 0.5 |
| B. | 0.05 |
| C. | 50 |
| D. | 500 |
| Answer» B. 0.05 | |
| 25. |
If temperature will increase, the conductivity of semiconductor will: |
| A. | remains the same |
| B. | decrease |
| C. | decrease rapidly |
| D. | increase |
| Answer» E. | |
| 26. |
Directions : Each of the next items consists of two statements, one labelled as the `Assertion (A)' and the other as 'Reason (R)' You are to examine these two statements carefully and select the answers to these items using the codes given below : Assertion (A): Concentration of acceptor atoms in the region between isolation islands will be much higher p*.than in the p type substrate in an integrated circuit.Reason (R): This is to prevent the depletion region ' of the reverse-biased isolation to substrate junction from extending into pi" type material. |
| A. | Both A and R are individually true and R is the correct explanation of A |
| B. | Both A and R are individually true but R is not the correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are individually true but R is not the correct explanation of A | |
| 27. |
Electrical conductivity, thermal conductivity and magnetic properties of ceramic material are |
| A. | very high all the time |
| B. | very low all the time |
| C. | dependent on the material |
| D. | ascertainable, instance to instance |
| Answer» C. dependent on the material | |