InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Which of the following statements concerning the depletion zone of an unbiased p-n junction is (are) true?A. The width of the zone is independent of the densities of the dopants (impurities).B. The widthof the zone is dependent on the densities of the dopantsC. The electric field in the zone is produced by ionised dopant atomsD. The electric field in the zone is provided by electrons in the conduction band and the holes in the valence band |
| Answer» Correct Answer - B | |
| 2. |
If a semiconductor has an intrinsic carrier concentration of `1.41 xx 10^(16)//m^(3)` when doped with `10^(21)//m^(3)` at room temperature will beA. `2 xx 10^(21)`B. `2 xx 10^(11)`C. `1.41 xx 10^(10)`D. `1.41 xx 10^(16)` |
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Answer» Correct Answer - D Doping wil increasse the number of electrons only nad not the holes. So, number of holes will be equal to number of intrinsic carrier concentration. `=1.41 xx 10^(16)//m^(3)` |
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| 3. |
In a `n`-type semiconductor, which of the following statement is true?A. Electrons are majority charge carriers and triavalent atoms are the dopants.B. Electrons are minority charge carriers and pentavaent atoms are the dopants.C. Holes are minority charge carriers and pentavalent atoms are the dopantsD. Holes are majority carriers and trivalent atoms are the dopants. |
| Answer» Correct Answer - C | |
| 4. |
The conductivity of a semiconductor increases with increase in temperature becauseA. Number density of free current carries increasesB. relaxation time increasesC. both number density of carriers and relaxation time increasesD. number density of current carriers increases, relaxation time decreases but effect of decreases in relaxation time is much less than increase in number density. |
| Answer» Correct Answer - D | |
| 5. |
If the resistivity of copper is `1.7 xx 10^(-6) Omega cm`, then the mobility of electrons in copper, if each atom of copper contributes one free electron for conduction, is [The amomic weight of copper is `63.54` and its density is `8.96 g//c c]` :A. 23.36 `cm^(2)`/VsB. 503.03 `cm^(2)`/VsC. 43.25 `cm^(2)`/VsD. 88 `cm^(2)`/Vs |
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Answer» Correct Answer - C Mobility of electron, `mu=simga/(ne)` …………..(i) Resistivity, `rho=1/sigma`………..(ii) From Eqs. (i) and (ii), we get `mu=1/(nep)`………….(iii) n=number of free electrons per unit volume `n=(N_(0) xx d)/("Atomic weight")` = `(6.023 xx 10^(23) xx 8.96)/(63.54)` `=8.5 xx 10^(22)`...............(iv) From Eqs. (iii) and (iv), we get `mu = (1)/(8.5 xx 10^(22) xx 1.6 xx 10^(-19) xx 1.7 xx 10^(-6))=43.25 cm^(2)//Vs` |
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| 6. |
A transistor is preferable to a triode valve when used in amplifier because it i) Can withstand large changes in tempratures ii) has a higher input impedance iii)can handle larger powers (iv) does not require powers Which of the above statements is correct?A. Only (i), (ii), and (iii) are correctB. Only (i), and (iii) are correctC. Only (ii) and (iv) are correctD. Only (vi) is correct. |
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Answer» Correct Answer - D A transistor is preferable to a triode valve when used in amplifier because it does not require a power. |
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| 7. |
What is the plate current in a diode valve under the space charge limited operation, when the plate potential is 60 V? In a diode valve, the plate current is 320 mA, then the plate potential is 240 V.A. 30 mAB. 20 mAC. 40 mAD. 10 mA |
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Answer» Correct Answer - C Using Child Langmuir law, `lpropt(60)^(3//3)` `320 prop(24)^(3//2)`...........(ii) Dividing Eq. (i) by Eq. (ii), we get `(320)/l = (4)^(3//2) rArr l=(320)/8 rArr l=40 mA` |
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| 8. |
When the plate voltage of a triode is 150 V, its cut-ff voltage is `-5V`. On increasing the plate voltate to 200V, the cut-off voltage can beA. `-4.5`VB. `-5.0`VC. 2.3 VD. `-6.66 V` |
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Answer» Correct Answer - D `V_(p_(1))=150V,V_(P_(2)) = 200V, V_(g_(1)) = -5V, V_(g_(2))=?` `mu`= amplification factor of a triode valve, it is a characteristic of valve remains constant. So long as `l_(p)` is constant. `thereforemu=-V_(P_(1))/(V_(q_(1)))=-V_(p_(2))/V_(g_(2))` `(150)/(-5) = (200)/(V_(g_(2)))` `V_(g_(2)) = -20/3 = -6.66V` |
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| 9. |
In a triode amplifier, the load resistance is equal to the plate resistance `r_(p)`. If `mu` is the amplification factor, the stage gain of the amplifier isA. `(mu)/2`B. `mu`C. `2mu`D. `(mu)/4` |
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Answer» Correct Answer - A `A=(mu)/(1+mu/2)` `R=r_(p)` `A=(mu)/2` |
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| 10. |
In BJT, maximum current flows in which of the following?A. Emitter regionB. Base regionC. Collector regionD. Equal in all the regions |
| Answer» Correct Answer - A | |
| 11. |
A tungsten emitter works at 2500 K. To increase the emission current density by 20%, how much change in the work function is required (Given, log2=0.3, log 3= 0.477)A. 0.016 eVB. 0.039 eVC. 2.54 eVD. 0.254 eV |
| Answer» Correct Answer - B | |
| 12. |
In Boolean algebra, A + B = Y implies thatA. sum of A and B is YB. Y exists when A exists or B exists or both A and B existC. Y exists only when A and B both existD. Y exist when A or B exist but not when both A and B exist |
| Answer» Correct Answer - D | |
| 13. |
If `A = B = 1`, then in terms of Boolean algebra the value of `A.B + A` is not equal to.A. B.A+BB. B+AC. BD. None |
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Answer» Correct Answer - D AB + A = `1.1 + 1 = 1+1 =1` Same is true for B. A+B as well as B+A. |
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| 14. |
The voltage gain of an amplifier state is 100. The gain expressed in db isA. 100B. 20C. 40D. 10 |
| Answer» Correct Answer - C | |
| 15. |
Zener breakdown in a semi-conductor diode occurs whenA. forward current exceeds certain valueB. reverse bias exceeds certain valueC. forward bias exceeds certain values.D. potential barrier is reduced to zero |
| Answer» Correct Answer - B | |
| 16. |
What is the dimensional formula of `sqrt(LC)` ?A. `(s)^(2)`B. volt-s/ampC. amp-s/voltD. s |
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Answer» Correct Answer - D At resonance, `omegaL=1/(omegaC)` `omega^(2) = 1/(LC)` `rArr omega=1/sqrt(LC)` `2pif=1/sqrt(LC)` Thus, dimension of `sqrt(LC)` is second. |
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| 17. |
For the given combination of gates, if the logic states of inputs `A,B,C,` are as follows `A=B=C=0` and `A=B=1, C=0` then the logic states of output `D` are A. 0,0B. 0,1C. 1,0D. 1,1 |
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Answer» Correct Answer - D The outpur D for the given combination `D=bar((A+B).C)=(bar(A+B)+bar(C))` If A=B=C=D, then `D=(bar(0+0)+bar0 = bar0+bar0=1+1+1` If A=B=1, C=0, then `D=(bar(1+1)) +bar0=bar1+bar0=0+1=1` |
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| 18. |
In common emitter amplifier, the `l_(c)/l_(e)` is 0.98, then the value of `beta` isA. 98B. 0.98C. 49D. None of these |
| Answer» Correct Answer - C | |
| 19. |
The triodes P and Q have the same amplification factor 40. Their plate resistances are `4kOmega` and `8kOmega`, respectively. If an amplifier circuit is designed using anyone of them and a load resistance is of `8kOmega`, the ratio of the voltage gain obtained from them will beA. `2:3`B. `4:3`C. `3:1`D. `1:2` |
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Answer» Correct Answer - B `mu=40`=amplification factor `mu_(p) = mu_(Q)=40` `r_(P)=4kOmega,r_(Q) = 8kOmega` `R_(L) = 8kOmega` Voltage gain for triode A `(muR_(L))/(r_(p)+R_(L))` For triode `P=A_(P) =(40 xx 8)/(4+8)` `A_(Q) = (40 xx 8)/(4+8)` `A_(P)/A_(Q) = ((40 xx 8)/(4+8))/((40 xx 8)/(8+8))=16/12 = 4/3` |
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| 20. |
In sample of pure silicon `10^(13) "atom"//cm^(3)` is mixed of phosphorus. If all doner atoms are active then what will be resistivity at `20^(@)C` if mobility of electron is `1200 cm^(2)//"Volt"` sec :-A. 0.5209 `Omega`-cmB. `5.209Omega`-cmC. `52.09 Omega`-cmD. `520.9 Omega`-cm |
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Answer» Correct Answer - D `1/rho = e(n_(e)mu_(e)+n_(h)mu_(h)=520.9Omega`-cm [By putting values] |
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| 21. |
The plate voltage of a triode is increased from 225 V to 250 V, the grid voltage is changed from 4 to `-4.7V` to maintain plate current constant. The amplification factor of the tube isA. 35.7B. 2C. 70D. 20 |
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Answer» Correct Answer - A `V_(p_(1))=225V, V_(p_(2))=250V, V_(g_(1))=-4V` `V_(g_(2)) = -4.7V` `mu=((DeltaV_(p))/(DeltaV_(g)))_(l_(p))=(25)/(0.7) = 35.7` |
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| 22. |
In the above circuit, if the polarity is reversed of battery, the current flowing would beA. 0 mAB. 2 mAC. 5 mAD. 10 mA |
| Answer» Correct Answer - A | |