Semiconductors & Communication · JEE Main previous year questions

In a semiconductor p-n diode, the doping concentrations on p-side and n-side are $10^{15}atoms/c{\mathrm{m}}^3$ and $10^{18}atoms/c{\mathrm{m}}^3$, respectively. Which one of the following statements is true ?

1. A.Widths of depletion region on either side of the interface are equal
2. B.The depletion region width is more on p-side compared to that in n-side
3. C.The depletion region width is more on n-side compared to that in p-side
4. D.No depletion region forms because of unequal doping concentrations on p and n-sides

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: A diode under reverse-biased condition provides very small current which is nearly independent of voltage until a critical limit at which the current increases drastically. Reason R: Below the critical voltage limit, only majority charge carriers flow which increases drastically above critical voltage. choose the correct answer from the options given below

1. A.Both A and R are true and R is the correct explanation of A
2. B.Both A and R are true but R is NOT the correct explanation of A
3. C.A is true but R is false
4. D.A is false but R is true

A diode has Zener voltage of $10\mathrm{V}$ and maximum power dissipation of $0.5\mathrm{W}$, then the minimum resistance to be used in series with this diode for safety when it is connected to a $25\mathrm{V}$ power supply is ____ $\Omega$.

1. A.Resistor in series with diode pointing towards Y
2. B.Diode pointing towards X in series with Zener diode pointing towards Y
3. C.Resistor in series with diode pointing towards X
4. D.Diode pointing towards X in series with Zener diode pointing towards X

1. A.17.6
2. B.18.8
3. C.20.15
4. D.11.7

1. A.AND Gate
2. B.OR Gate
3. C.NOR Gate
4. D.NAND Gate

1. A.100
2. B.10
3. C.1000
4. D.4000

1. A.
2. B.
3. C.
4. D.

1. A.1000
2. B.0011
3. C.0100
4. D.1101

1. A.$0\mathrm{V}$
2. B.$+5\mathrm{V}$
3. C.$-5\mathrm{V}$
4. D.$10\mathrm{V}$

The Boolean expression $Y=A\bar{B}C+\bar{A}\bar{C}$ can be realised with which of the following gate configurations. A. One 3-input AND gate, 3 NOT gates and one 2-input OR gate, one 2-input AND gate B. One 3 -input AND gate, 1 NOT gate, One 2 -input NOR gate and one 2 -input OR gate C. 3 -input OR gate, 3 NOT gates and one 2 -input AND gate Choose the correct answer from the options given below:

1. A.B, C Only
2. B.A, B, C Only
3. C.A, B Only
4. D.A, C Only

Consider a n-type semiconductor in which ${\mathrm{n}}_{\mathrm{e}}$ and ${\mathrm{n}}_{\mathrm{h}}$ are number of electrons and holes, respectively. (A) Holes are minority carriers (B) The dopant is a pentavalent atom (C) ${\mathrm{n}}_{\mathrm{e}}{\mathrm{n}}_{\mathrm{h}}\ne {\mathrm{n}}_i^2$ (where ${\mathrm{n}}_i$ is number of electrons or holes in semiconductor when it is intrinsic form) (D) ${\mathrm{n}}_{\mathrm{e}}{\mathrm{n}}_{\mathrm{h}}⩾{\mathrm{n}}_i^2$ (E) The holes are not generated due to the donors Choose the correct answer from the options given below :

1. A.(A), (B), (E) only
2. B.(A), (C), (E) only
3. C.(A), (B), (C) only
4. D.(A), (C), (D) only

A vessel with square cross-section and height of $6\text{ m}$ is vertically partitioned. A small window of $100{\text{ cm}}^2$ with hinged door is fitted at a depth of $3\text{ m}$ in the partition wall. One part of the vessel is filled completely with water and the other side is filled with the liquid having density $1.5\times 10^3{\text{ kg/m}}^3$. What force one needs to apply on the hinged door so that it does not get opened ? (Acceleration due to gravity $=10{\text{ m/s}}^2$ )

Consider the following statements : A. The junction area of solar cell is made very narrow compared to a photo diode. B. Solar cells are not connected with any external bias. C. LED is made of lightly doped p-n junction. D. Increase of forward current results in continuous increase of LED light intensity. E. LEDs have to be connected in forward bias for emission of light. Choose the correct answer from the options given below :

1. A.A, C, E Only
2. B.B, E Only
3. C.A, C Only
4. D.B, D, E Only

1. A.(C) and (E) only
2. B.(A) and (D) only
3. C.(B), (D) and (E) only
4. D.(B), (C) and (E) only

A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is $1.42\text{ eV}$. The wavelength of light emitted from the LED is :

1. A.1243 nm
2. B.875 nm
3. C.650 nm
4. D.1400 nm

The acceptor level of a p-type semiconductor is $6\mathrm{eV}$. The maximum wavelength of light which can create a hole would be : Given $\mathrm{hc}=1242\mathrm{eV}\mathrm{nm}$.

1. A.$407\mathrm{nm}$
2. B.$103.5\mathrm{nm}$
3. C.$414\mathrm{nm}$
4. D.$207\mathrm{nm}$

1. A.OR gate
2. B.NAND gate
3. C.NOR gate
4. D.AND gate

A bus moving along a straight highway with speed of $72\text{ km/h}$ is brought to a halt within $4s$ after applying the brakes. The distance travelled by the bus during this time (Assume the retardation is uniform) is ________ $m$.

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than $660\text{ nm}$. The band gap of photodiode is found to be $\left(\frac{\mathrm{X}}{8}\right)\text{eV}$. The value of $\mathrm{X}$ is : (Given, $\mathrm{h}=6.6\times 10^{-34}\text{Js},\mathrm{e}=1.6\times 10^{-19}\text{C}$ )

1. A.11
2. B.13
3. C.15
4. D.21

1. A.0
2. B.$30\text{ mA}$
3. C.$20\text{ mA}$
4. D.$50\text{ mA}$

1. A.$3.3\text{ mA}$
2. B.$10\text{ mA}$
3. C.$5.5\text{ mA}$
4. D.$7\text{ mA}$

A particle is moving in a circle of radius $50\text{ cm}$ in such a way that at any instant the normal and tangential components of it's acceleration are equal. If its speed at $t=0$ is $4\text{ m/s}$, the time taken to complete the first revolution will be $\frac{1}{\alpha }\left[1-e^{-2\pi }\right]\text{s}$, where $\alpha =$ _________.

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : The angular speed of the moon in its orbit about the earth is more than the angular speed of the earth in its orbit about the sun. Reason (R) : The moon takes less time to move around the earth than the time taken by the earth to move around the sun. In the light of the above statements, choose the most appropriate answer from the options given below :

1. A.Both (A) and (R) are correct but (R) is not the correct explanation of (A)
2. B.(A) is correct but (R) is not correct
3. C.Both (A) and (R) are correct and (R) is the correct explanation of (A)
4. D.(A) is not correct but (R) is correct