Electronics

SAIL Electronics and Electrical engineering objective type questions with answers for practice, SAIL model questions for practice,SAIL free solved sample placement papers of previous years

1.  To neglect a voltage source, the terminals across the source are

(A)  open circuited

(B)  short circuited     (Ans)

(C)  replaced by some resistance

(D)  replaced by an inductor

 

2. Current I₀ in the given circuit will be

(A)  10 A

(B)  3.33 A     (Ans)

(C)  20 A

(D)  2.5 A

Solution :  R_T= 2 + 2 || [1 + (2 || 2)]

= 2 + 2 || (1 + 1)

= 2 + 2 || 2 = 2 + 1 = 3 Ω

So    I =  40 A
               3

By current division I₀= 1 * 1 * 40  =  10 A
                                 2    2    3        3

I₀= 3.33 A                               

 

3.  In a resonant circuit, the power factor at resonance is

(A)  zero

(B)  unity     (Ans)

(C)  0.5

(D)  1.5

 

4.  In the given circuit voltage V is reduced to half. The current will become

(A)  I/2    (Ans)

(B)  2 I

(C)  1.5 I

(D)  I / √R² + (X_L+ X_C)²

Solution :   I a V if V reduced half current becomes   I.
                                                                        2

 

5.  The function          3 s           has
                        (s + 1) (s + 2)

(A)  one zero, two poles    (Ans)

(B)  no zero, one pole

(C)  no zero, two poles

(D)  one zero, no pole

 Solution :  G (s) =           3s            has one zero at s = 0 and two poles at s =  - 1,  - 2.
                            (s + 1) (s + 2)

 

6.  One electron volt is equivalent to

(A)  1.6 * 10^-10 J

(B)  1.6 * 10^-13 J

(C)  1.6 * 10^-16 J

(D)  1.6 * 10^-19 J    (Ans)

 

7.  Which of the following is donor impurity element ?

(A)  Aluminium

(B)  Boron

(C)  Phosphorous    (Ans)

(D)  Indium.

 

8.  The diameter of an atom is of the order

(A)  10^-6 m

(B)  10^-10 m   (Ans)

(C)  10^-15 m

(D)  10^-21 m

 

9.  The following Figure represents

(A)  LED    (Ans)

(B)  Varistor

(C)  SCR

(D)  Diac

 

10.  If the d.c. valve of a rectified output is 300 V and peak to peak ripple voltage is 10 V, the ripple factor is

(A)  1.18%

(B)  3.33%   (Ans)

(C)  3.36%

(D)  6.66%

 Solution :  rms value of output

= √300² + 10² = 300.166 V

Average value = 300 V

Form factor      RMS value     = 300.166 = 1.00055.
                  Average value          300

Ripple factor = √(Form factor)² - 1

 = √(1.0005)² - 1 = 0.0333

= 3.33%.

 

11.  Full wave rectifier output has ripple factor of

(A)  1.11    (Ans)

(B)  1.21

(C)  1.41

(D)  1.51

 

12.  In a common base connection I_E= 2 mA, I_C= 1.9 mA. The value of base current is

(A)  0.1 m    (Ans)

(B)  0.2 mA

(C)  0.3 mA

(D)  zero

Solution :  I_E = 2 mA     I_C= 1.9 mA

I_b = I_E  - I_C= (2 - 1.9) = 0.1 mA.

 

13.  For the action of transistor the base region must be

(A)  P-type material

(B)  N-type material

(C)  very narrow     (Ans)

(D)  highly doped

 

14.  Compared to a CB amplifier the CE amplifier has higher

(A)  current amplification

(B)  output dynamic resistance

(C)  leakage current

(D)  input dynamic resistance

(E)  all of the above    (Ans)  

 

15.  When a transistor is biased to cut-off its Y is

(A)  0.5

(B)  0

(C)  1.0    (Ans)

(D)  0.8