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ECE :: Exam Questions Paper

  1. Radiation resistance of an antenna is 54 Ω and loss resistance is 6 Ω. If antenna has power gain of 10, then directivity is:

  2. A.
    9
    B.
    11.11
    C.
    data not sufficient
    D.
    10

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  3. If the power spectral density of stationary random process is a sine-squared function of frequency, the shape of its autocorrelation is

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  5. The inverse of given Laplace transform is

  6. A.
    sin t
    B.
    cos t
    C.
    et
    D.
    e2t

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  7. In a 4 bit weighted resistor D/A converter, the resistor value corresponding to LSB is 32 kΩ. The resistor value corresponding to MSB will be

  8. A.
    32 KΩ
    B.
    16 KΩ
    C.
    8 KΩ
    D.
    4 KΩ

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  9. Suppose that the modulating signal is m(t) = 2cos (2pfmt) and the carrier signal is xC(t) = AC cos(2pfct), which one of the following is a conventional AM signal without over modulation?

  10. A.
    x(t) = Acm(t)cos(2pfct)
    B.
    x(t) = Ac [1 + m(t)]cos (2pfct)
    C.
    D.
    x(t) = Accos(2pfmt)cos(2pfct) + Acsin(2pfmt)sin(2pfct)

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  11. What are the values of Emax and Emin displayed on the oscilloscope, when a 1 kV P-P carries is modulated to 50%?

  12. A.
    2 kV, 0.5 kV
    B.
    1 kV, 0.5 kV
    C.
    0.75 kV, 0.25 kV
    D.
    0.5 kV, 1.5 kV

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  13. Consider the common emitter amplifier shown below with the following circuit parameters: β = 100, gm = 0.3861 A/V, r0 = ∞ rp = 259 Ω, Rs = 1 kΩ, RB = 93 kΩ, RC = 250 Ω, RL = 1 kW, C1 = ∞ and C2 = 4.7mF.

    The resistance seen by the source Vs is

  14. A.
    258 Ω
    B.
    1258 Ω
    C.
    93 kΩ
    D.

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  15. As the temperature increases the mobility of electrons __________ .

  16. A.
    decreases because the number of carries increases with increased collisions
    B.
    increases because the number of carries decreases with decreased collisions
    C.
    remains same
    D.
    none of the above

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  17. Consider the following

    1. Maximum energy of electrons liberated photoelectrically is independent of light intensity
    2. Maximum energy of electrons liberated photoelectrically varies nonlinearly with frequency of incident light.

  18. A.
    (1) is true and (2) is false
    B.
    (1) and (2) both are true
    C.
    (1) is false and (2) is true
    D.
    (1) and (2) both are false

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  19. When phase-lag compensation is used in a system, then gain cross over frequency, bandwidth and undamped frequency are respectively

  20. A.
    Increased, Increased, Increased
    B.
    Increased, Increased, Decreased
    C.
    Increased, Decreased, Decreased
    D.
    Decreased, Decreased, Decreased

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