2012 December UGC NET Solved Question Paper in Electronic Science, Paper II

1. For a JFET IDSS = 8 mA and peak voltage Vp = –8V, what will be the drain current for gate to source voltage of –2V?

(A) 4.5 mA

(B) 8 mA

(C) 16 mA

(D) 12 mA

Answer: (A)

 

Answer: (C)

 

3. A tree in a network has a

(A) Closed path

(B) No closed path

(C) No nodes

(D) No branches

Answer: (B)

 

Answer: (B)

 

5. Which is a three-terminal negative voltage regulator IC?

(A) 78 XX

(B) IC 723

(C) LM 317

(D) 79 XX

Answer: (D)

 

6. Three identical stages have overall upper 3 dB frequency of 2 KHz and lower 3 dB frequency of 20 Hz. What is the value of fH of each stage?

(A) 13 KHz

(B) 26 KHz

(C) 39 KHz

(D) 52 KHz

Answer: (C)www.netugc.com

 

Answer: (D)

 

Answer: (B)

 

9. Microprocessor 8086 allows floating point arithmetic calculations in

(A) Maximum mode

(B) Minimum mode

(C) Both maximum and minimum modes

(D) Neither in maximum nor in minimum mode

Answer: (A)

 

10. Which of the following chip is used in 8085 microprocessor 3-chip configuration?

(A) IC 8255

(B) IC 8155

(C) IC 8251

(D) IC 8257

Answer: (B)

11. C Language is a _________

(A) High level language

(B) Low level language

(C) Machine level language

(D) Middle level language

Answer: (D)

 

12. In a ‘C’ language expression, if the following expressions appear, which will be evaluated first?

(A) x + y

(B) x . y

(C) (x + y)

(D) x/y

Answer: (C)

 

Answer: (A)

 

Answer: (B)

 

15. A 20 kW carrier is sinusoidally modulated by two carriers corresponding to modulation index of 30% and 40% respectively. The total radiated power is

(A) 25 kW

(B) 22.5 kW

(C) 45.0 kW

(D) 35.0 kW

Answer: (B)

 

16. ASCII code has 128 characters, which are binary coded. If a computer generates 106 characters per second, then minimum band width required to transmit this signal will be

(A) 1.4 mbps

(B) 14 mbps

(C) 7 mbps

(D) 0.7 mbps

Answer: (C)

 

17. When the current through SCR is greater than holding current, then the voltage across the SCR is

(A) 1.4 V

(B) 0 V

(C) Supply voltage

(D) Half the load voltage

Answer: (A)

 

18. Dispersion shifted wave length is

(A) 800 nm

(B) 1550 nm

(C) 1310 nm

(D) 1200 nm

Answer: (B)

 

19. The most suitable instrument for the measurement of voltage is

(A) DVM

(B) Analog voltmeter

(C) CRO

(D) DMM

Answer: (C)

 

20. The characteristic polynomial of a system is

q(s) = 2s5 + s4 + 4s3 + 2s2 + 2s + 1

The system is

(A) Stable

(B) Marginally stable

(C) Unstable

(D) Oscillatory

Answer: (D)

Directions:

Q. No(s) 21 to 30: The following items consist of two statements, one labelled the “Assertion (A)” and the other labelled the “Reason (R)”. You are to examine these two statements carefully and decide if the Assertion (A) and the Reason (R) are individually true and if so, whether the Reason is a correct explanation of the Assertion. Select your answers to these items using the codes given below and mark your answer accordingly.

Codes:

(A) Both (A) and (R) are true and (R) is the correct explanation of (A).

(B) Both (A) and (R) are true, but (R) is not correct explanation of (A).

(C) (A) is true, but (R) is false.

(D) (A) is false, but (R) is true.

 

21. Assertion (A): Tunnel diode provides oscillations in the microwave region.

Reason (R): The equivalent RC model of tunnel diode gives frequency in the microwave region.

Answer: (C)

 

22. Assertion (A): The roots of the denominator of a network function decide its stability.

Reason (R): The poles on realax is determine the damping factor of the system.

Answer: (A)

 

23. Assertion (A): The fast changing inputs do not depend upon slew rate property of an OPAMP.

Reason (R): Schmitt trigger does not work on the slew rate property of an OPAMP.

Answer: (D)

 

24. Assertion (A): A parallel comparator ADC requires in – built no. of comparators = 2N -1.

Reason (R): The speed of parallel comparator is limited by the speed of comparator.

Answer: (A)

 

25. Assertion (A): Microcontrollers are preferred in Real time applications.

Reason (R): The on chip I/O integration has no bearing on the speed of microcontroller.www.netugc.com

Answer: (C)

 

26. Assertion (A): In ‘FORTRAN’ pointers are provided.

Reason (R): Pointers help to work with actual physical addresses.

Answer: (D)

 

27. Assertion (A): Divergence theorem is applicable for both static and time varying fields.

Reason (R): It is used to find enclosed charge from the knowledge of either – D or – E.

Answer: (A)

 

28. Assertion (A): The back e.m.f. of a d.c. motor depends upon series winding and armature resistance.

Reason (R): When there is no load, the back emf is minimum.

Answer: (C)

 

29. Assertion (A): By using wavelength division, multiplexing the capacity of an optical fibre can be enhanced.

Reason (R): The separation between two adjacent channels in WDM is of the order of 50nm.

Answer: (C)

 

30. Assertion (A): The sign of all terms in the first row of Routh’s array are checked, for stability considerations.

Reason (R): The number of sign changes equals the no. of roots on the right hand side of s-plane.

Answer: (D)

 

31. Consider the following four transistors

1. CE mode

2. CC mode

3. MOSFET

4. FET

The correct order in which, the input impedance increases is

(A) 1, 2, 4, 3

(B) 1, 2, 3, 4

(C) 1, 3, 2, 4

(D) 4, 3, 2, 1

Answer: (A)

 

32. The correct order in which the power dissipation in transistor in power amplifiers decreases:

1. Class A

2. Class C

3. Class B

4. Class AB

The correct order is

(A) 1, 3, 2 and 4

(B) 1, 3, 4 and 2

(C) 1, 2, 3, 4

(D) 4, 3, 2, 1

Answer: (B)

 

33. The following are the interrupts of 8085 microprocessor:

1. INTR

2. TRAP

3. RST 7.5

4. RST 5.5

The correct order in which these interrupts will be executed, if arrive simultaneously:

(A) 1, 2, 3, 4

(B) 2, 3, 1, 4

(C) 2, 3, 4, 1

(D) 4, 1, 2, 3

Answer: (C)

 

34. The following are the oscillators:

1. Crystal

2. Weinbridge

3. Colpitt’s

4. Tunnel diode oscillator

The correct sequence of decreasing order of the frequency of oscillation will be:

(A) 4, 1, 3, 2

(B) 4, 1, 2, 3

(C) 4, 3, 2, 1

(D) 4, 2, 3, 1

Answer: (A)

 

35. Following are the controllers:

1. On-off

2. PID

3. PI

The correct order of the decrease in error output is

(A) 1, 2, 3

(B) 1, 3, 2

(C) 3, 2, 1

(D) 3, 1, 2

Answer: (B)

 

Directions: Q. Nos. 36 to 45:In the following questions, match List – I and List – II and select the correct answer using the codes given below the lists:

 

36. List – I                              List – II

a. P-N junction diode              i. base width modulation

b. BJT                                      ii. AGC

c. FET                                                 iii. –2 mV/0C

d. MOSFET                            iv. Low power consumption

Codes:

      a b c d

(A) i ii iii iv

(B) ii i iii iv

(C) iv i ii iii

(D) iii i ii iv

Answer: (D)

 

Answer: (A)

 

Answer: (B)

 

39. List – I                              List – II

a. Combinational logic            i. Sequential circuits

b. Counters                              ii. ROM

c. LIFO                                   iii. DVM

d. State diagram                      iv. Shift register

Codes:

      a b c d

(A) ii iii iv i

(B) ii iv iii i

(C) i ii iii iv

(D) iv iii ii i

Answer: (A)

 

40. List – I      List – II

a. 8085            i. variable port addressing

b. 8086            ii. Serial communication

c. 8279            iii. Register bank

d. 8051            iv. 2-key lockout

Codes:

      a b c d

(A) i ii iii iv

(B) iii ii i iv

(C) ii iv i iii

(D) ii i iv iii

Answer: (D)

 

41. List – I                  List – II

a. while (1)                  i. on-off control implementation

b. paranthesis              ii. Infinite

c. Switch-case             iii.Change of precedence

d. If-then                     iv. Multiple processing

Codes:

      a b c d

(A) i ii iii iv

(B) iii iv ii i

(C) ii iii iv i

(D) ii iv iii i

Answer: (C)

 

Answer: (B)

 

43. List – I                              List – II

a. QPSK                                  i. deviation

b. Hamming code                    ii. I.F.

c. Superhetrodyne                   iii. Error correction

d. Frequency modulation        iv. 900

Codes:

       a b c d

(A) iv i ii iii

(B) iv ii iii i

(C) ii iii iv i

(D) iv iii ii i

Answer: (D)

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44. List – I                              List – II

a. relaxation oscillator             i. PWM

b. S.M.P.S.                              ii. triac

c. population inversion            iii. UJT

d. bi-directional control          iv. Laser

Codes:

       a b c d

(A) iii i iv ii

(B) iii ii i iv

(C) iv i ii iii

(D) iii i ii iv

Answer: (A)

 

45. List – I                                          List – II

a. Strain measurement                         i. Pt-100

b. temperature measurement               ii. load cell

c. Lissajous figures                              iii. Bio-medical signals

d. E.M.G.                                            iv. C.R.O.

Codes:

      a b c d

(A) i ii iv iii

(B) ii i iv iii

(C) iii ii i iv

(D) iii iv ii i

Answer: (B)

 

Read the passage below and answer the questions 46 to 50, that follows based on your understanding of the passage:

Many instruments require dc power of their operation. This power is available from a portable cell; however, the power output is low besides other problems. AC power is continuously and easily available, so it is convenient to use it. However, ac power must be converted into dc power.

The devices such as half-wave, full wave and bridge rectifiers convert bi-directional voltage to uni-directional voltage. However, the output has large ripple contents. Filters are used to reduce the ripple significantly. Various filters circuits and L, C, LC and CLC. The power supply with rectifier and filter is still unregulated.

The output of such power supplies varies with variations in a.c. mains voltage, load current and temperature.

In order to maintain the output at constant level, voltage or current regulation is necessary. This is obtained by using series or shunt feedback. In addition to regulation, the power supply also requires protection e.g. overload, over current or short circuit protection. Pre- regulation is also carried out to improve the stability.

Regulators can be designed by using discrete components. However, IC regulators are also available. These regulators have facilities like:

(i) Voltage / current boosting

(ii) Thermal shut-down

(iii) Floating point to facilitate higher output voltage

(iv) Switching regulator to reduce the power dissipation.

 

46. The minimum supply voltage to operate IC 7815 is

(A) 15 V

(B) 17 V

(C) 25 V

(D) 40 V

Answer: (C)

 

47. In low voltage, low current model, IC 723 gives output voltage in the range of

(A) 2 to 7 V

(B) 5 to 10 V

(C) 0 to 10 V

(D) 0 to 7 V

Answer: (A)

 

48. For a d.c. output of 30 V, from a full wave rectifier, the PIV rating of the diode should be minimum

(A) 50 V

(B) 75 V

(C) 100 V

(D) 200 V

Answer: (C)

 

49. The critical inductance in mains power supply ensures that the current through ‘L’ never becomes zero. For this, critical value of inductance is

(A)RL/310

(B)RL/450

(C)RL/620

(D)RL/942

Answer: (D)

 

50. In series pass voltage regulator using zener diode, the function of zener diode is a.

(A) Voltage regulator

(B) Voltage comparator

(C) Breakdown diode

(D) Temperature compensator

Answer: (B)

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