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ECE :: Exam Questions Paper

  1. With a line charge along z-axis the field intensity is E = ; which of the following figure shows an exact field distribution?

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  3. The logic function f(A, B, C) = m(0, 2, 4, 5, 6) can be represented by :

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

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  5. In amplitude modulation, carrier signals A cos ωt has its amplitude A modulated in proportion with message bearing (low frequency) signal m(t). The magnitude of m(t) is chosen to be __________ .

  6. A.
    less than 1
    B.
    less than or equal to 1
    C.
    more than 1
    D.
    none of these

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  7. The logic realized by the circuit shown in figure below is

  8. A.
    F = A - C
    B.
    F = A + C
    C.
    F = B ⊙ C
    D.
    F = B ⊕ C

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  9. An image uses 512 x 512 picture elements. Each of the picture elements can take any of the 8 distinguishable intensity levels. The maximum entropy in the above image will be

  10. A.
    2097152 bits
    B.
    648 bits
    C.
    786432 bits
    D.
    144 bits

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  11. A tachometer has a sensitivity of 4 V/1000 rpm. Express the gain constant of the tachometer in the units volts/(rad/sec).

  12. A.
    0.0489
    B.
    0.0381
    C.
    2
    D.
    none of these

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  13. Consider the signal x(n) = 1 + sinn + 3 cosn + cos . Then Fourier series coefficients are __________ .

  14. A.
    1, - j, + j, j, - j
    B.
    1, + j, - j, - j , + j
    C.
    1, 3 - j, 3 + j, j, - j
    D.
    1, 3 + j, 3 - j, - j, + j

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  15. A certain system has transfer function a is a parameter. Consider the standard negative unity feedback configuration as shown below.

    Which of the following statements is true?

  16. A.
    The closed loop system in never stable for any value of a a
    B.
    For some positive values of a, the closed loop system is stable, but not for all positive values
    C.
    For all positive values of a, the closed loop system is stable
    D.
    The closed loop system is stable for all values of a, both positive and negative

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  17. If a signal f(t) has energy E, the energy of the signal f(2t) is equal to __________ .

  18. A.
    E
    B.
    E/2
    C.
    E/4
    D.
    2E

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  19. For a npn BJT transistor fβ is 1.64 x 108 Hz. Cμ = 10-14 F; Cp = 4 x 10-13 F and DC current gain is 90. Find fT and gm (fβ = cut off frequency, Cμ = capacitance, Cp = parasitic capacitance, gm = transconductance, fT = gain BW product)

  20. A.
    fT = 1.47 x 1010 Hz ; gm = 38 milli mho
    B.
    fT = 1.64 x 108 Hz ; gm = 30 milli mho
    C.
    fT = 1.47 x 109 Hz ; gm = 38 mho
    D.
    fT = 1.33 x 1012 Hz; gm = 0.37 m-mho

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