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ECE :: Exam Questions Paper

  1. The signal flow graph of a system is shown in figure. The transfer function of the system is :


  2. The Laplace transform of the given waveform is

  3. A.
    (1 - e-s + e-2s)
    B.
    (1 - e-s + e-2s)
    C.
    (1 - 2e-s + e-2s)
    D.
    (1 - 2e-s)

  4. With respect to the following 555 timer circuit what will be the value of RA and R such that the LED turns on for a duration of 10 ms every time it receives negative trigger pulse. LED operating current = 20 mA, Vf = 1.4 V, Vo on = 13.4 V and C = 0.22 nf

  5. A.
    41.4 KΩ, 600 Ω
    B.
    45 KΩ, 630 Ω
    C.
    43.5 KΩ, 580 Ω
    D.
    44.9 KΩ, 600 Ω

  6. The region between a pin of parallel perfectly conducting planes of infinite extent is y and z directions is partially filled with a dielectric as shown below.

    A 30 GHz TE10 wave is incident on the air-dielectric interface. The value of reflection coefficient at the interface is


  7. Consider the program segment written for 8085 based system:
    LXI S, FFFFH
    MVI A, 00H
    MVI B, 0FH
    SUB B
    CNC GOLOC
    MVI A, FFH
    where in the program subroutine labelled ''GOLOC'' introduces delay of 28 T-states only. How many T-states are required to execute above program statement?

  8. A.
    41
    B.
    69
    C.
    44
    D.
    Indeterminate

  9. A discrete random variable X takes values from 1 to 5 with probabilities as shown in the table. A student calculates the mean of X and 3.5 and her teacher calculates the variance of X as 1.5. Which of the following statements is true?

  10. A.
    Both the student and the teacher are right
    B.
    Both the student and the teacher are wrong
    C.
    Both the student is wrong but the teacher is right
    D.
    The student is right but the teacher is wrong

  11. The effective modulation index is:

  12. A.
    0.91287
    B.
    0.8306
    C.
    1
    D.
    none of these

  13. Consider Continuous time system y(t) = x(t) - . For the system to be linear response ax1(t) + bx2(t) should be ay1(t) + by2(t) with relation between constant 'a' and 'b' as __________ .

  14. A.
    a + b = 2
    B.
    a x b = 1
    C.
    a = b
    D.
    a + b = 1

  15. Hari (H), Gita (G), Irfan (I) and Saira (S) are sibiligs (i.e. brothers and sisters). All were born on 1st January. The age difference between any two successive siblings (that is born one after another) is less than 3 years. Given the following facts:
    (i) Hari's age + Gita's age > Irfan's age + Saira's age.
    (ii) The age difference between Gita and Saira is 1 year. However, Gita is not the oldest and Saira is not the youngest.
    (iii) There are not twins.
    In what order were they born (Oldest first)?

  16. A.
    HSIG
    B.
    SGHI
    C.
    IGSH
    D.
    IHSG

  17. If a signal f(t/2) has energy is E/n then energy of the signal f(nt) is equal to __________ (n is constant)

  18. A.
    E/2n2
    B.
    2E/n2
    C.
    E/n2
    D.
    2En2