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.
| 201. |
An `NPN`-transistor circuit is arranged as shown in figure. It is A. A common base amplifier circuitB. A common emitter amplifier circuitC. A common collector amplifier circuitD. Neither of the above |
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Answer» Correct Answer - B Because emitter `(N)` is common to both, base `(P)` and collector `(N)`. |
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| 202. |
The given graph represents `V-I` characterstic for a semiconductor device Which of the following satetement is correct?A. It is `V-I` characterstic for solar cell where point A represented open circuit voltage and point `B` short circuit currentB. It is for a solar celll and points `A` and `B` represent open circuit voltage and current, respectivelyC. It is for a photodiode and points `A` and `B` represent open circuit voltage and current, respectivelyD. It is for an `LED` and point `A` and `B` represents open circuit voltage and short circuit respectively. |
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Answer» Correct Answer - A The given graph represents `V-I` characterstics of solar cell. |
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| 203. |
Assertion: Television signals are recieved throgh sky-wave propagation. Reason: The ionosphere reflects em wave of frequencies greater than a critical frequency.A. If both the assertion and reason are true and reason is a true explantion of the assertion.B. If both the assertion and reason are true but the reason is not true the correct explantion of the assertion.C. If the assertion is true but reason falseD. If both the assertion and reason are false. |
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Answer» Correct Answer - D In sky-wave propagation the radio waves which have frequency between `2 MHz` to `3MHz`, are reflected back to the ground by the ionosphere. But radio waves having frequency greater than `30 MHz` cannot be reflected by the ionosphere because at this frequency they penetrate the ionosphere. It makes the sky-wave propagation less reliable for propagation of `TV` signal having frequency greater than `30 MHz`. Critcal frequency is defined as the highest frequency that is returened to the earth by the ionosphere. Thus, above this frequency a wave whether it is electronagnetic will penetrate the ionosphere and is not reflected by it. |
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| 204. |
To obtain a `P`-type `Si` semiconductor, we need to dope pure `Si` withA. AluminiumB. PhosphorusC. OxygenD. Germenium |
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Answer» Correct Answer - A Aluminium is trivalent impurity. |
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| 205. |
In a common base amplifier circuit, calculate the change in base current if that in the emitter current is `2mA` and `alpha=0.98`A. `0.04 mA`B. `1.96mA`C. `0.98 mA`D. `2 mA` |
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Answer» Correct Answer - A `Deltai_(c)=alpha Delta i_(e) =0.98xx2=1.96 mA` `:. Deltai_(b)=Deltai_(e)-Deltai_(e)=2-1.96=0.04 mA` |
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| 206. |
For a transistor ampliflier in common emiter configuration for load imperdance of `1 k Omega (h_(fe) = 50 and h_(oe) = 25)` the current gain isA. `-5.2`B. `-15.7`C. `-24.8`D. `-48.78` |
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Answer» Correct Answer - D In common emitter configuration current gain `A_(1)=(-h_(fe))/(1+h_(oe)R_(L))=(-50)/(1+25xx10^(-6)xx10^(3))=-48.78`. |
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| 207. |
Which one is forward biase?A. B. C. D. None of these |
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Answer» Correct Answer - B In forward biasing `P`-side is connected with positive terminal and `N`-side with negative terminal of the battery. |
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| 208. |
Given below are four logic tage symboles. Those for `OR, NOR` and `NAND` are respectively: A. `1,4,3`B. `4,1,2`C. `1,3,4`D. `4,2,1` |
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Answer» Correct Answer - C The double is added to `OR` gate to represent the `NOR` gate and the same is true for `AND` and `NAND` gates. |
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| 209. |
Assertion: The number of electrons in a `p`-type silicon semiconductor is less than the number of electrons ina pure silicon semiconductor at room temperature. Reason: It is due to law of mass action.A. If both the assertion and reason are true and reason is a true explantion of the assertion.B. If both the assertion and reason are true but the reason is not true the correct explantion of the assertion.C. If the assertion is true but reason falseD. If both the assertion and reason are false. |
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Answer» Correct Answer - A According to law of mass-action, `n_(i)^(2)=n_(e)n_(h)` For `p`-type semiconductor, number of electrons is less than the number of electrons in a pure silicon semiconductor that is for `p`-type semiconductor, `n_(e) lt n_(h)`. |
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| 210. |
Figure shows a piece of semiconductor (pure one) `S` in series with a variable resistor `R` and a source of constant voltage `V. S` is heated and the current is kept constant by adjustment `R`. Which of the following factors will decrease during this process? `(1)` The drift velocity of the conduction electrons in `S`. `(2)` The `DC` resistance of `S` `(3)` The number of conduction electrons in `S`. which of the following is correct?A. only `1`B. `1` and `2`C. `1,2` and `3`D. only `3` |
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Answer» Correct Answer - B Note that drift velocity in semiconductors in affected by an increases in temperature in the same way as in metals i.e., reduced due to an increases in the number of collisions with the lattice ions. Which vibrate with greater amplitude at a higher temperature? |
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| 211. |
A pure semiconductor behaves slightly as a conductor atA. Room temperatureB. Low temperatureC. High temperatureD. Both `(b)` and `(c)` |
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Answer» Correct Answer - A At room temperature some covelent bond breaks and semiconductor behaves slightly as a conductor. |
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| 212. |
The forbidden energy band gap in conductors, semiconductors and insulators are `EG_(1), EG_(2)` and `EG_(3)` respectively. The relation among them isA. `EG_(1)=EG_(2)=EG_(3)`B. `EG_(1) lt EG_(2) lt EG_(3)`C. `EG_(1) gt EG_(2) gt EG_(3)`D. `EG_(1) lt EG_(2) gt EG_(3)` |
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Answer» Correct Answer - B In insulators, the forbidden energy gap is very largest, in case of semiconductor it is moderate and in conductors it is moderate and in conductors the energy gap is zero. |
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| 213. |
The forbidden gap in the energy bands of germanium at room temperature is aboutA. `1.1 eV`B. `0.1 eV`C. `0.67 eV`D. `6.7 eV` |
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Answer» Correct Answer - C `DeltaE_(g)(Germanium)=0.67 eV` |
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| 214. |
The width of forbidden gap in silicon crystal is `1.1 eV`. When the crystal is converted into a `N`-type semiconductor the distance of Fermi level from conduction band isA. Greater than `0.55 eV`B. Equal to `0.55 eV`C. Lesser than `0.55 eV`D. Equal to `1.1 eV` |
| Answer» Correct Answer - C | |
| 215. |
In a `n`-type semiconductor, which of the following statement is true?A. Electrons are majority carriers and trivalent atoms are dopantsB. Electrons are minority carriers and pentavalent atoms are dopantsC. Holes are minority carriers and pentavalent atoms are dopantsD. Holes are majority carriers and trivalent atoms are dopants |
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Answer» Correct Answer - C In a `n`-type semiconductor holes are minority carriers and pentavalent atoms are dopants. |
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| 216. |
The output `(X)` of the logic circuit shown in figure will be A. `X=bar(bar(A)).bar(bar(B))`B. `X=bar(A.B)`C. `X=A.B`D. `X=bar(A+B)` |
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Answer» Correct Answer - C `X=bar(bar(AB))=A.B` |
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| 217. |
The valence of an impurity added to germanium crystal in order to convert it into a `P`-type semiconductor isA. `6`B. `5`C. `4`D. `3` |
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Answer» Correct Answer - D `Ge+underset("impurity")("Trivalent") to underset("semiconductor") (P-type)` |
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| 218. |
The velence of the impurity atom that is to the be added to garmenium crystal so as to meke it a `N`-type semiconductor, isA. `6`B. `5`C. `4`D. `3` |
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Answer» Correct Answer - B `Ge+underset ("impurity")("pentaevelent") to underset("semiconductor") (N-type)` |
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| 219. |
The impurity atom added to germenium to make it `N`-type semiconductor isA. ArsenicB. IridiumC. AluminiumD. Iodine |
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Answer» Correct Answer - A For `N`-type semiconductor, the impurity should be pentavalent. |
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| 220. |
In `P`-type semiconductor germenium is dopped withA. BoronB. GalliumC. AluminiumD. All of these |
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Answer» Correct Answer - D All are trivalent in nature. |
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| 221. |
Which impurity is dopped in `Si` to from `N`-type semiconductor?A. `Al`B. `B`C. `As`D. None of these |
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Answer» Correct Answer - C Because As is pentavalent impurity. |
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| 222. |
A semiconductor dopped with a donor impurity isA. `P`-typeB. `N`-typeC. `NPN` -typeD. `PNP`-type |
| Answer» Correct Answer - B | |
| 223. |
A `Ge` specimen is dopped with `Al`. The concentration of acceptor atoms is `~10^(21) at oms//m^(3)`. Given that the intrinsic concentration of electron hole pairs is `~10^(19)//m^(3)`, the concentration of electron in the speciman isA. `10^(15)//m^(3)`B. `10^(17)//m^(3)`C. `10^(4)//m^(3)`D. `10^(2)//m^(3)` |
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Answer» Correct Answer - B From law of mass-action `n_(i)^(2)=n_(e)xxn_(h)` Where `n_(i)` is concentration of electron-hole pair and `n_(h)` is concentration of acceptor or holes. Given, `n_(i)=10^(19) per m^(3),n_(h)=10^(21) per m^(3)` `(10^(19))^(2)=n_(e)xx10^(21)` `implies n_(e)=(10^(38))/(10^(21))=10^(17) per m^(3)` |
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| 224. |
Assertion: We can measure the potential barrier of a `PN` junction by putting a sensitive voltmeter across its terminals. Reason: The current through the `PN` junction is not same in forward and reversed bias.A. If both the assertion and reason are true and reason is a true explantion of the assertion.B. If both the assertion and reason are true but the reason is not true the correct explantion of the assertion.C. If the assertion is true but reason falseD. If both the assertion and reason are false. |
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Answer» Correct Answer - D We cannot measure is potential barrier of a `PN`-junction by connecting a sensitive voltmenter across its terminals because in the depletion region, there are no free electrons and holes and in the absence of forward biasing, `PN` -junction offers infinite resistance. |
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| 225. |
`N`-type semiconductors will be obtained, when germanium is dopped withA. PhosphorusB. AlluminiumC. ArsenicD. Both `(a)` and (c)` |
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Answer» Correct Answer - D Phosphorus and Arsenic both are pentavalent. |
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| 226. |
Barrier potential of a `p-n` junction diode does not depend onA. Diode designB. TemperatureC. Forwards biasD. Dopping density |
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Answer» Correct Answer - A The barrier potential depends upon temperature, for ward bias and dopping density. |
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| 227. |
A pure semiconductor has equal electron and hole concentration of `10^(6)m^(-3)`. Dopping by indium increases `n_(h)` to `4.5xx10^(22)m^(0k3)`. What is `n_(e)` in the dopped semiconductor?A. `10^(6)m^(-3)`B. `10^(22)m^(-3)`C. `(10^(32))/(4.5xx10^(22))m^(-3)`D. `4.5xx10^(22)m^(-3)` |
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Answer» Correct Answer - A `n_(e)h_(e)=n^(2)` or `h_(e)=(n^(2))/(n_(h))=(10^(16)xx10^(16))/(4.5xx10^(22))` `=(10^(32))/(4.5xx10^(22))m^(-3)` |
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| 228. |
An `N`-type and `P`-type silicon can be obtained by dopping pure silicon withA. Arsenic and PhosphorusB. Indium and AluminiumC. Phosphorus and IndiumD. Aluminium and Boron |
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Answer» Correct Answer - C Phosphorus is a pentavalent while indium is trivelent. |
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| 229. |
A semiconductor is known to have an electron concentric of `8xx10^(13)//cm^(3)` and hole concentration of `5xx10^(12)//cm^(3)`. The semiconductor isA. `N`-typeB. `P`-typeC. IntrinsicD. Insulator |
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Answer» Correct Answer - A In `N`-type semiconductor, free electrons are the majority charge carriers. |
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| 230. |
Assertion: Electron has higher mobility than hole in a semiconductor. Reason: Mass of electron is less than the mass of hole.A. If both the assertion and reason are true and reason is a true explantion of the assertion.B. If both the assertion and reason are true but the reason is not true the correct explantion of the assertion.C. If the assertion is true but reason falseD. If both the assertion and reason are false. |
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Answer» Correct Answer - A The ratio of the velocity to the applied field is called the mobility. Since electron is lighter than holes, they move faster in applied field than holes. |
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| 231. |
Assertion: The resistivity of a semiconductor increases with temperature. Reason: The atoms of a semiconductor vibrate with larger amplitude at higher temperature therby increasing it resistivity.A. If both the assertion and reason are true and reason is a true explantion of the assertion.B. If both the assertion and reason are true but the reason is not true the correct explantion of the assertion.C. If the assertion is true but reason falseD. If both the assertion and reason are false. |
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Answer» Correct Answer - D Solids whose electrical conductivity is intermediate between conductor and insulator are called semiconductors/ Carbon, silicon and germanium are example of semiconductors. The temperature coefficient of resistance of semiconductors is negative that is their electrical resistance decreases (or conductivity increases) with rise in temperature. |
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| 232. |
The barrier potential of a `p-n`-junction depends on (i) Type of semiconductor material (ii) Amount of doping (iii) Temperature which of the following is correct?A. `(i)` and `(ii)` onlyB. `(ii)` onlyC. `(ii)` and `(iii)` onlyD. `(i),(ii)` and `(iii)` |
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Answer» Correct Answer - D The barrier potential `p-n` junction depends on amount of doping type of semiconductor material and temperature. |
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| 233. |
When the `P` end of `P-N` junction is connected to the negative terminal of the battery and the `N` end to theA. A conductorB. An insulatorC. A superconductorD. A semiconductor |
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Answer» Correct Answer - B In this condition `P-N` junction is reverse biased. |
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| 234. |
A `P`-type semiconductor can be obtained by addingA. Arsenic to pure siliconB. gallium to pure siliconC. Antimony to pure germeniumD. Phosphorus ot pure germanium |
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Answer» Correct Answer - B `Ga` has a valency of `3`. |
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| 235. |
Regarding a semiconductor which one of the following statements is wrong?A. There are no free electrons at room temperatureB. There are no free electron at `0 K`C. The number of free electrons increases with arise of temperatureD. The charge carries are electron and holes |
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Answer» Correct Answer - A At room temperature, few bonds breaks and electron hole pair generates inside the semiconductor. |
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| 236. |
Choose the correct statementA. When we heat a semiconductor its resistance increasedB. When we heat a semiconductor its resistance decreasedC. When we cool a semiconductor to `0K` then it becomes supper conductorD. Resistance of a semiconductor is independent of temperature |
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Answer» Correct Answer - B With rise in temperature, conductivity of semiconductor increases while resistance decreases. |
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