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Topic:- ELEC MSC S2

1. The equation of the plane through the points (1, -1,2), (1, 1, -2) and (-1, 1,2) is

   [Question ID = 1584]

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   1. x + 3y + 2z - 2 = 0
   2. x - y + 2z - 2 = 0
   3. 2x + 2y + z - 2 = 0
   4. x + y - z - 2 = 0

   Correct Answer :-

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   • 2x + 2y + z - 2 = 0

2. Unit vector perpendicular to A = 3î + î + 2k and B = 2î – 2j + 4k vectors is

   [Question ID = 1585]

   1. ±(3î -j - k)/v14

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   2. ±(î+j+k)/v3
   3. ±(î-j+k)/v3
   4. ±(î-j-k)/v3

   Correct Answer :-

   • ±(î-j-k)/v3

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3. The two complex numbers Z1 = 2 + i2/v3 and Z2 = v3 + i. The argument of Z1/Z2 in degree is

   [Question ID = 1586]

   1. 0°
   2. 90°

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   3. 30°
   4. 60°

   Correct Answer :-

   • 0°

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4. The value of the definite integral ? sin x dx from 0 to p/2 is

   [Question ID = 1587]

   1. 1
   2. 0
   3. p

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   4. -p

   Correct Answer :-

   • 0

5. If we differentiate the f(x) = x^x then df/dx

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   [Question ID = 1588]

   1. 1 + logx
   2. -x^x(1 + logx)
   3. x^x(1 + logx)
   4. x^x(logx)

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   Correct Answer :-

   • x^x(1 + logx)

6. The absolute maximum and minimum values points of x³ - 6x² + 9x - 7 in [0 5] are

   [Question ID = 1589]

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   1. the point of maxima is 3 and the point of minima is 5
   2. the point of maxima is 5 and the point of minima is 0
   3. the point of maxima is 5 and the point of minima is 3
   4. There is no maxima and minima points in [0 5]

   Correct Answer :-

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   • the point of maxima is 5 and the point of minima is 3

7. The Laplace transform of given unit step function f(t-ß) = {0 t < ß, 1 t > ß} is

   [Question ID = 1590]

   1. e^-2s/ß

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   2. e^-ßs/s
   3. -e^-2s/s
   4. e^-2s

   Correct Answer :-

   • e^-ßs/s

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8. If 2 and 4 are the eigen values of square matrix A then the Eigen values of A^T are

   [Question ID = 1591]

   1. 0.5, 0.25
   2. 2, 4

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   3. 4, 16
   4. 3, 2

   Correct Answer :-

   • 2, 4

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9. The system of equation x - 2y + z = 0, 2x - y + 3z = 0 and ? x + y - z = 0 has non zero solution, if ? is

   [Question ID = 1592]

   1. ? = 0.4
   2. ? = -2
   3. ? = 2

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   4. ? = -0.8

   Correct Answer :-

   • ? = -0.8

10. If A is skew-Hermitian, then (iA) is

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    [Question ID = 1593]

    1. Skew-symmetric
    2. Symmetric
    3. Hermitian
    4. Skew-Hermitian

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    Correct Answer :-

    • Hermitian

11. The integrating factor of the differential equation dy/dx + y/x = x³ - 3 is

    [Question ID = 1594]

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    1. 1/x
    2. x log x
    3. x
    4. log x

    Correct Answer :-

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    • x

12. The solution of dy/dx - y tan x = y² sec x is given by:-

    [Question ID = 1595]

    1. y^-1 = sinx + C₁ cos x

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    2. y^-1 = cosx + c₃ sinx
    3. y^-1 = - cosx + c₁ sin x
    4. y^-1 = -sinx + c₂ cos x

    Correct Answer :-

    • y^-1 = -sinx + c₂ cos x

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13. The family of conic represented by the solution of the differential equation (4x + 3y +1) dx + (3x+2y+1) dy = 0 is

    [Question ID = 1596]

    1. Parabolas
    2. Circle

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    3. Ellipses
    4. Hyperbola

    Correct Answer :-

    • Hyperbola

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14. The function f(x)= x³- 6x² + 9x + 25

    [Question ID = 1597]

    1. maxima at x = 1 and a minima at x = 3
    2. a maxima at x = 3 and a minima at x = 1
    3. no maxima, but a minima at x = 1

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    4. a maxima at x = 1,but no minima

    Correct Answer :-

    • maxima at x = 1 and a minima at x = 3

15. Consider an optical fiber of 75 µm diameter, core index n₁ = 1.5, and cladding index n₂ = 1.49 for operation at ? = 1.31 µm. How many modes does this fiber support?

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    [Question ID = 1598]

    1. 244
    2. 312
    3. 484
    4. 188

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    Correct Answer :-

    • 484

16. When a LED has 2 V applied to its terminals, it draws 100 mA and produces 4 mW of optical power. The LED conversion efficiency from electrical to optical power is:-

    [Question ID = 1599]

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    1. 3%
    2. 4%
    3. 5%
    4. 2%

    Correct Answer :-

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    • 2%

17. Number of electron-hole pairs generated divided by the number of photons is:-

    [Question ID = 1600]

    1. Dark current

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    2. Quantum response
    3. Photo sensitivity
    4. Quantum efficiency

    Correct Answer :-

    • Quantum efficiency

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18. If the refractive index of a media is 1.5, the velocity of light in the medium is:-

    [Question ID = 1601]

    1. 3×10⁸ m/s
    2. 1.5×10⁸ m/s

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    3. 1×10⁸ m/s
    4. 2×10⁸ m/s

    Correct Answer :-

    • 2×10⁸ m/s

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19. In C language, what is the output of the following code

    int main()
    { int c; printf("%i",c);
    }
    

    [Question ID = 1602]

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    1. 1
    2. 0
    3. error
    4. 4

    Correct Answer :-

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    • 0

20. In C language, what is the output of the following code

    int main()
    { int i = 4; printf("%d%d",i,i++);
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    }
    

    [Question ID = 1603]

    1. 54
    2. 45
    3. 44

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    4. 55

    Correct Answer :-

    • 54

21. In C language, what is the output of the following code

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    int main()
    { int a = 63, b = 9; printf("%d",a>>a/b-2);
    }
    

    [Question ID = 1604]

    1. 1

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    2. 2
    3. 3
    4. None of these

    Correct Answer :-

    • 1

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22. main()
    { int x; x = 4; while (x > 1) { printf("%d",x); x=x-1; }
    }
    

    [Question ID = 1605]

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    1. 4323
    2. 432
    3. 4321
    4. 3215

    Correct Answer :-

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    • 432

23. In C "switch" statement, each case instance value must be:-

    [Question ID = 1606]

    1. constant

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    2. Variable
    3. Special symbol
    4. None of these

    Correct Answer :-

    • constant

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24. If mobility of an electrons in Si at 300 K is 0.16 m²/V.s then the diffusion coefficient of electrons is:-

    [Question ID = 1607]

    1. 20.7 x 10^-4 m²/s
    2. 62.1 x 10^-4 m²/s

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    3. 6.4 x 10^-2 m²/s
    4. 41.4 x 10^-4 m²/s

    Correct Answer :-

    • 41.4 x 10^-4 m²/s

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25. If an electric field of 45 V/m is applied to a semiconductor sample whose Hall coefficient is 0.04 m³/C then the current density in the sample is (Given: µ_n = 0.36 m²/V)

    [Question ID = 1608]

    1. 203 A/cm²
    2. 814 A/m²
    3. 414 A/m²

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    4. 650 A/cm²

    Correct Answer :-

    • 414 A/m²

26. Radiation recombination lifetime is 0.3 ns from a contact. If the minority carrier mobility is 8000 cm²/V.s at 300 K then the diffusion length for the electron is:-

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    [Question ID = 1609]

    1. 2.50 µm
    2. 1.25 µm
    3. 5.00 µm
    4. 7.98 µm

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    Correct Answer :-

    • 2.50 µm

27. Consider a 10 µm diameter p-n junction fabricated in Si. If donor density is 10¹⁵ /cm³ and acceptor density is 10¹⁶ /cm³ then built in potential in the p-n junction is (Given: intrinsic carrier concentration for Si = 1.75 × 10¹⁰ /cm³)

    [Question ID = 1610]

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    1. 0.31 V
    2. 1.12 V
    3. 1.42 V
    4. 0.63 V

    Correct Answer :-

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    • 0.63 V

28. In an n-type GaAs crystal at 300 K, the electron concentration varies as n(x) = 1.5 × 10¹⁵ exp(-x/L) /cm². If the electron diffusion co-efficient is 250 cm²/s then the diffusion current density at x = 0 is (where L = 1.5µm and x > 0)

    [Question ID = 1611]

    1. 1.5 kA/cm²

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    2. 1.0 kA/cm²
    3. 10.0 kA/cm²
    4. 0.4 kA/cm²

    Correct Answer :-

    • 0.4 kA/cm²

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29. In a MOSFET the transfer characteristics are used to determine which of the following device parameter?

    [Question ID = 1612]

    1. threshold voltage and output resistance
    2. threshold voltage and transconductance

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    3. transconductance and output resistance
    4. transconductance and channel length modulation

    Correct Answer :-

    • threshold voltage and transconductance

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30. The maximum voltage gain obtained from FET having g_m = 5ms and r_d = 20kO is

    [Question ID = 1613]

    1. 100
    2. 10
    3. 0

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    4. infinity

    Correct Answer :-

    • 100

31. The drain of n-channel MOSFET is shorted to the gate and threshold voltage is 1.5V. If the drain current (I_D) is 2 mA for V_GS = 2.5 V then for V_GS = 3.5 V the I_D is

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    [Question ID = 1614]

    1. 2 mA
    2. 4 mA
    3. 8 mA
    4. 1 mA

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32. If a BJT has base current 250 µA and emitter current collector current

    [Question ID = 1615]

    1. 14.75 µ? and 99
    2. 14.75 A and 59

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    3. 14.75 µ? and 99.8
    4. 14.75 mA and 59

    Correct Answer :-

    • 14.75 mA and 59

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33. For the following Lissajous figure, the ratio of frequencies of signals applied to two inputs of CRO is

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