BSNL Tech Assistant Placement Papers

               BSNL JTO Technical Assistant previous years solved question paper

BSNL JTO Technical Assistant previous years solved question papers of electronics and electrical engineering.. For the preparation of BSNL Exam General Ability -20 marks questions, Basic Engineering-90 Specialisation-90 marks questions. Practice model question papers

1.  For reflection co-efficient |r| = 1/2 VSWR is

(A)  2

(B)  3    (Ans)

(C)  C

(D)  8

2.  Radiation resistance of a half wave dipole is

(A)  73 ?  (Ans)

(B)  377 ?

(C)  300 ?

(D)  50 ?

3. Which of the following is not Maxwell's equation ?

(A)  B = ?H

(B)  E = D/?

(C)  E = J/?

(D)  E = ?D  (Ans)

4.  A medium is called isotropic when

(A)  ? is zero

(B)  ? is a scalar constant   (Ans)

(C)  ? = ?

(D)  ? = ??

5.  Which of the following is not a wide band antenna

(A)  marconi   (Ans)

(B)  helical

(C)  rhombic

(D)  folded dipole

6.  The wave which "lies down and dies" is called

(A)  ground wave   (Ans)

(B)  sky wave

(C)  space wave

(D)  spherical wave

7.  When cathode is positive with respect to anode in an SCR, the number of p-n junction is

(A)  1

(B)  2  (Ans)

(C)  3

(D)  4

8.  The impulse response and the excitation function of a linar time invariant causal system are shown in Fig. (a) and (b) respectively. The output of system at t = 2 sec is equal to

(A)  0

(B)  1/2   (Ans)

(C)  3/2

(D)  2

Solution :  y (y) = f x (t) h (t - t) dt

  Out Put     = 1/2 * 2 1/2 = 1/2

9.  The initial contents of the 4-bit serial-in-parallel-out right-shift, Shift Register shown in Fig.is 0110. After three clock pulses are applied, the contents of the Shift Register will be

(A)  0000

(B)  0101

(C)  1010   (Ans)

(D)  1111

Solution :  4-bit SIPO

1 XOR (1, 0) = 1  1011

2 XOR (1, 1) = 0  0101

3 XOR (0, 1) = 1  1010

contents will be 1010.

10.  Fig. shows the circuit of a gate in the Resistor Transistor Logic (RTL) family. The circuit represents a

(A)  NAND

(B)  AND

(C)  NOR

(D)  OR    (Ans)

    V_i1    V_i2    V_x    V₀    Q₁       Q₂     Q₃

    L      L      H    L    OFF   OFF   ON

    L      H      L    H    OFF   ON   OFF

    H      L      L    H    ON    OFF   OFF

    H      H      L    H    ON    ON    OFF

The circuit represent an OR. Hence choice is d. 

11.  The logic realized by the circuit shown in Fig.

(A)  F = A . C

(B)  F = A + C    (Ans)

(C)  F = B . C

(D)  F = B + C

F = does not depend on B.

F = A C + A C = A ?  C

12.  A Lissajous pattern, as shown in Fig below, is observed on the screen of a CRO when voltage of frequencies f_x and f_y are applied to the x and y plates respectively. f_x : f_y is then equal to

(A)  3 : 2

(B)  1 : 2   (Ans)

(C)  2 : 3

(D)  2 : 1

 Solution :  f_x/f_f= Points of tangency to vertical line/Points of tangency to horizontal line = 1/2

or f_x : f_y = 1 : 2

13.  In the transistor circuit shown in Fig. below, collector-to-ground voltage is + 20 V. Which of the following is the probable cause of error ?

(A)  Collector-emitter terminals shorted

(B)  Emitter to ground connection open    (Ans)

(C)  10 k ? resistor open

(D)  collector-base terminals shorted