EC Engineering MCQs​

Electronics and Communication Engineering  Test Paper

Choose the correct answer

1. The output power of an audio power amplifier is 12 W, which is approximately

a) 20 dBm                   b) 41 dBm                   c) 62 dBm                   d) 86 dBm

2. The bandwidth of a wide-band amplifier to reproduce a pulse faithfully depends on

a) Width of the pulse                                       b) Rise time of the pulse        
c) Frequency of the pulse                               d) All of these

3. When the peak power is 10 kW and average power is 800 W, then duty cycle is

a) 0.008%                    b) 0.08%                      c) 0.8%                        d) 8%

4. The primary purpose of helix in a travelling wave tube is to

• a) Reduce the axial velocity of RF field      
• b) Ensure broadband operation
• c) Reduce the noise figure                           
• d) Prevent the electron beam from spreading in the long tube

5. A parabolic antenna is commonly used at

a) 38 kHz                    b) 19 kHz                    c) 455 kHz      d) None of these

6. If the input signal to noise ratio of a system is 30, and the output signal to noise ratio is 3, then the noise figure F of the system is

a) 90                            b) 10                            c) 900              d) 33

7.         The unit of loudness is:
a) phon                        d) sone                        c) decibel        d) mel

8.         Soundproof door in studios generally provides attenuation of the order of:
a) 60 dB                      b) 50 dB                      c) 30 dB          d) 15 dB

9.         An FM signal with a deviation d is passed through a mixer and has its frequency reduced five fold. The deviation in the output of mixer will be:
a) 5d                            b) d                              c) d/5               d) indeterminate

10.       Top loading is used with an antenna in order to increase its
a) effective height       b) bandwidth               c) Beamwidth  d) input capacitance

11. What is the aspect ratio of HDTV application?

a) 4:3                           b) 3:4                           c) 9:16             d) 16:9

12. Why are radiators stacked vertically on a TV tower?

a) for wideband matching                               b) To obtain desired gain                               
c) For omni-directional pattern                       d) None of these

13. What is the minimum field strength required for UHF TV transmission?

a) 110 dBmV/m          b) 65 dBmV/m                       c) 55 dBmV/m            d) 45 dBmV/m

14.What is the tape speed in Beta-cam VTR?

a) 90 mm/sec              b) 101.5 mm/sec         c)65 mm/sec   d)110 mm/sec

15. What is the duration of active period of a line in CVS (Composite Video Signal)?

a) 62 msec                   b) 27 msec                   c) 108 msec                 d) 52 msec

16. In a 3-wire circuit, the loads on the Y and B phases draw 1 A each from the line and the R phase is open circulated. What is the current flowing through the neutral conductor?

a) 0 A                          b) 1 A                          c) 2 A                          d) 3 A

17. A PERT chart helps in:

• Identifying the critical activities of a Project.
• Knowing the earliest possible completion date of each activity.
• Knowing the lag permissible for each activity
• All the above.

18.The interior of an air-conditioning duct is lined with:

a) Mineral wool           b) Common straw       c) Cotton         d) Thin concrete slabs.

19. The horse power of a Diesel Engine is decided by:

a) the bore                   b) no. of cylinders       c) the rpm       d) all of these

Answers:  EC Engineering MCQs​

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