BSNL Electronics and Electrical Questions
BSNL Model Question papers with answers and detailed explanations to prepare for upcoming JTO and Technicians examintion
BSNL electronics and electrical solved question papers
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
 RE 2001 - Part A - Qno. 2_1.png )
(A) 10 A
(B) 3.33 A (Ans)
(C) 20 A
(D) 2.5 A
Solution : RT= 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
 RE 2001 - Part A - Qno. 4_1.png)
(A) I/2 (Ans)
(B) 2 I
(C) 1.5 I
(D) I / √R2+ (XL+ XC)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
Image - BSNL- MB (J.T.O.) RE 2001 - Part A - Qno. 9
(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 IE= 2 mA, IC= 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 : IE = 2 mA IC= 1.9 mA
Ib= IE - IC= (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
16. An ideal voltage amplifier should have
(A) Ri = 0, R0 = 0
(B) Ri = 0, R0 = ¥
(C) Ri = ¥, R0 = 0 (Ans)
(D) Ri = 0, R0 = ¥
17. Barichausen criterion for sustained oscillator is
(A) Aβ = 1 Ð00 (Ans)
(B) Aβ = 0
(C) Aβ = 1 Ð1800
(D) A = 1/√β
18. The value of plastic capacitance for a triode may range from
(A) 2 μF to 12 μF
(B) 20 μF to 120 μF
(C) 2 pF to 12 pF (Ans)
(D) 20 pF to 120 pF
19. A colpitts oscillator uses
(A) tapped coil
(B) inductive feedback
(C) tapped capacitance (Ans)
(D) no tuned LC circuit
20. A typical frequency for a RC feedback oscillator is
(A) 1 KHz (Ans)
(B) 100 MHz
(C) 1000 MHz
(D) 1 GHz
21. In pulse transmitter the ratio of time on to time off is called
(A) efficiency
(B) duty cycle (Ans)
(C) base
(D) bandwidth
22. FM broadcast band generally lies in
(A) LF
(B) HF
(C) VHF (Ans)
(D) SHF
23. The following filter is generally used in SSB generation
(A) active filter
(B) mechanical filter (Ans)
(C) LC filter
(D) crystal filter
24. Which is a digital communication system ?
(A) FM
(B) AM
(C) PCM (Ans)
(D) PAM
25. A transistor is basically an amplifying device for
(A) power
(B) voltage
(C) current (Ans)
(D) all of these
