MCQOPTIONS
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MCQOPTIONS
This section includes 1085 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 951. |
The effective refraction index of the ionosphere for radio wave is |
| A. | more than unity |
| B. | less than unity |
| C. | equal to unity |
| D. | either more or less than unity depending on the electron concentration |
| Answer» C. equal to unity | |
| 952. |
A square corner reflector is used in |
| A. | radio astronomy |
| B. | tv broadcast |
| C. | point to point communication |
| D. | all of the above |
| Answer» E. | |
| 953. |
A broadside array consisting of 200 cm wavelength with 10 half-wave dipole spacing 10 cm. And if each array element feeding with 1 amp. current and operating at same frequency then find the radiated power |
| A. | 730 W |
| B. | 73 W |
| C. | 100 W |
| D. | None |
| Answer» B. 73 W | |
| 954. |
For a rectangular waveguide (a x b, a > b) to support only the TE10 mode at wavelength which one of the following pairs of in equalities is to be satisfied? |
| A. | b < λ < 2b; λ > 2a |
| B. | b < λ < 2b; λ < 2a |
| C. | a < λ < 2b; λ < 2a |
| D. | a < λ < 2b; λ > 2a |
| Answer» E. | |
| 955. |
The magnetic field due to current I equals |
| A. | I/2 pr |
| B. | I/4 pr |
| C. | I2/2 pr |
| D. | I2/4 pr |
| Answer» B. I/4 pr | |
| 956. |
The troposphere extends from earth surface to a height of |
| A. | 15 km |
| B. | 90 km |
| C. | 150 km |
| D. | 200 km |
| Answer» B. 90 km | |
| 957. |
Half power point directions for broadside is |
| A. | 60° |
| B. | 30° |
| C. | 45° |
| D. | at any angle |
| Answer» B. 30¬∞ | |
| 958. |
When the phase velocity of an EM wave depends on frequency in any medium the phenomenon is called |
| A. | scattering |
| B. | polarisation |
| C. | absorption |
| D. | dispersion |
| Answer» C. absorption | |
| 959. |
Which of the wave remains unaffected whether it is a day or night? |
| A. | Sky wave |
| B. | Ground wave |
| C. | Tropospheric wave |
| D. | Space wave |
| Answer» C. Tropospheric wave | |
| 960. |
The effective height of a vertical radiator can be increased by |
| A. | loading with lumped inductance |
| B. | supporting on an insulator |
| C. | capacitive loading |
| D. | giving input more power |
| Answer» D. giving input more power | |
| 961. |
Find the radiation resistance of an antenna of length λ/10 meter? |
| A. | 8 Ω |
| B. | 780 Ω |
| C. | 7.8 Ω |
| D. | 78 Ω |
| Answer» D. 78 Œ© | |
| 962. |
A uniform plane wave is one in which |
| A. | x = 0 |
| B. | . |
| C. | and are perpendicular |
| D. | and lie in a plane |
| Answer» E. | |
| 963. |
Antenna used for T.V. broadcasting is |
| A. | long dipole |
| B. | metal horn |
| C. | crossed dipole |
| D. | log periodic |
| Answer» D. log periodic | |
| 964. |
For frequency up to 1650 kHz, the transmitting antenna is used a |
| A. | parabolic dish |
| B. | vertical antenna |
| C. | yagi antenna |
| D. | turnstile antenna |
| Answer» C. yagi antenna | |
| 965. |
Charge needed within a unit sphere centred at the origin for producing a potential field, |
| A. | 12 pc |
| B. | 60 pc |
| C. | 120 pc |
| D. | 180 pc |
| Answer» D. 180 pc | |
| 966. |
Which of the following should dominant wave have? |
| A. | Lowest cut off frequency |
| B. | Highest cut off frequency |
| C. | No attenuation |
| D. | No phase shift |
| Answer» B. Highest cut off frequency | |
| 967. |
The intrinsic impedance of free space |
| A. | increases with increase of frequency |
| B. | decreases with increase of frequency |
| C. | is independent of frequency |
| D. | none |
| Answer» D. none | |
| 968. |
An open coil has |
| A. | zero resistance and inductance |
| B. | zero resistance and high inductance |
| C. | infinite resistance and zero inductance |
| D. | infinite resistance and normal inductance |
| Answer» D. infinite resistance and normal inductance | |
| 969. |
A square corner reflector is used in which of the following? |
| A. | TV broadcast |
| B. | Point-to-point communication |
| C. | Radio astronomy |
| D. | All of the above |
| Answer» E. | |
| 970. |
When a plane wave travelling in free space is incident normally on a medium having εr = 4.0, then fraction of power transmitted into the medium is given by |
| A. | 43716 |
| B. | 43497 |
| C. | 43525 |
| D. | 43621 |
| Answer» B. 43497 | |
| 971. |
What will happen to a bird sitting on a conductor? |
| A. | It will die of shock |
| B. | It will not die of shock because its claws are insulated |
| C. | It will not die because it is insulated from earth and other conductors |
| D. | None of the above |
| Answer» D. None of the above | |
| 972. |
End fire array has narrow bandwidth. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 973. |
Radiation resistance of half-wave dipole (λ/2) antenna is in free space |
| A. | 73 Ω |
| B. | 120 p |
| C. | 36.5 Ω |
| D. | 70 Ω |
| Answer» B. 120 p | |
| 974. |
The I/P impedance of a long short circuited section of a loss less transmission line is |
| A. | zero |
| B. | inductive |
| C. | capacitance |
| D. | infinite |
| Answer» C. capacitance | |
| 975. |
‚àá2 is |
| A. | vector |
| B. | scalar |
| C. | depend on direction |
| D. | none |
| Answer» C. depend on direction | |
| 976. |
In a medium if ε, μ and σ are constant throughout the medium, then it is known as |
| A. | perfect vacuum |
| B. | distributed medium |
| C. | homogeneous medium |
| D. | dielectric medium |
| Answer» D. dielectric medium | |
| 977. |
The refractive index of E layer at frequency of 81 N |
| A. | 0 |
| B. | ‚àû |
| C. | 1 |
| D. | 0.5 |
| Answer» B. ‚àû | |
| 978. |
The radiation pattern of Hertzian dipole in the plane perpendicular to dipole is a |
| A. | null |
| B. | circle |
| C. | figure of eight |
| D. | none of the above |
| Answer» D. none of the above | |
| 979. |
End fire coupler is formed |
| A. | when two equal radiators are operated in phase quadrature at a distance of λ/4 apart |
| B. | when two equal radiators are operated in parallel at a distance of λ/4 apart |
| C. | when two equal radiators are operated in phase quadrature at a distance of λ/2 apart |
| D. | none of the above |
| Answer» B. when two equal radiators are operated in parallel at a distance of Œª/4 apart | |
| 980. |
Which of the following is a better propagation mode to propagate television frequency modulation and radar signals? |
| A. | Satellite communication |
| B. | Ground propagation |
| C. | Polarized communication |
| D. | None of the above |
| Answer» B. Ground propagation | |
| 981. |
If short-circuited and open circuited impedances are 5 ohms and 20 ohms, then characteristic impedance is |
| A. | 1 ohms |
| B. | 10 ohms |
| C. | 25 ohms |
| D. | 100 ohms |
| Answer» C. 25 ohms | |
| 982. |
A unipole is also known as |
| A. | omnidirectional radiator |
| B. | unidirectional radiator |
| C. | line radiator |
| D. | none of the above |
| Answer» B. unidirectional radiator | |
| 983. |
A wavelength of 1 mm could be expected in |
| A. | VLF |
| B. | HF |
| C. | EHF |
| D. | SHF |
| Answer» D. SHF | |
| 984. |
When a wave is incident from the more dense into a less dense medium at an angle equal to or exceeding the critical angle, the wave suffers total internal __________ . |
| A. | reflection |
| B. | refraction |
| C. | transmission |
| D. | none of the above |
| Answer» C. transmission | |
| 985. |
After reflection from a plane conducting surface, the apparent velocity of electromagnetic wave becomes greater than the velocity of light in free space is called |
| A. | conventional velocity |
| B. | phase velocity |
| C. | propagation velocity |
| D. | group velocity |
| Answer» C. propagation velocity | |
| 986. |
A plane wave is characterized by the wave is |
| A. | linearly polarized |
| B. | circularly polarized |
| C. | elliptically polarized |
| D. | unpolarized |
| Answer» D. unpolarized | |
| 987. |
The electric flux and field intensity inside a conducting sphere is |
| A. | minimum |
| B. | maximum |
| C. | uniform |
| D. | zero |
| Answer» E. | |
| 988. |
Zoning is used with a dielectric antenna in order to |
| A. | permit pin-point focusing |
| B. | reduce the bulk of the lens |
| C. | increase the bandwidth of the lens |
| D. | correct the curvature of the wavefront from a horn that is too short |
| Answer» B. reduce the bulk of the lens | |
| 989. |
The relative permeability is taken as unity for which of the following? |
| A. | Air |
| B. | Cobalt |
| C. | Vacuum |
| D. | Bismuth |
| Answer» B. Cobalt | |
| 990. |
A broadside array is shown in figure in which the elements are placed at equal distances. The direction of maximum radiation is represented by |
| A. | AA |
| B. | BB |
| C. | CC |
| D. | DD |
| Answer» B. BB | |
| 991. |
When a coil consisting of single turn rotates at a uniform speed in a magnetic field, the induced e.m.f. is |
| A. | changing |
| B. | reversing |
| C. | steady |
| D. | alternating |
| Answer» E. | |
| 992. |
Television signals are propagated as ground waves. |
| A. | 1 |
| B. | |
| C. | f(z) = f0e-jβz |
| D. | f(z) = f0 sin βz |
| Answer» B. | |
| 993. |
The wave in wave guide has |
| A. | group velocity inversely proportional to wavelength |
| B. | larger frequency than in the free space |
| C. | diminishing wavelength than in the free space |
| D. | larger wavelength than in the free space |
| Answer» E. | |
| 994. |
For a quarter wave transformer, characteristic impedance is related with input and load impedances as |
| A. | Z0 = ZR/ZS |
| B. | Z0 = ZR . ZS |
| Answer» C. | |
| 995. |
In a four element Yagi-Uda antenna |
| A. | there is one driven element, one director and two reflectors |
| B. | there is one driven element, two directors and one reflector |
| C. | there are two driven elements, one director and two reflectors |
| D. | all the 4 elements are driven element |
| Answer» C. there are two driven elements, one director and two reflectors | |
| 996. |
A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls find cut off wavelength for dominant mode. |
| A. | 4 cm |
| B. | 1 cm |
| C. | 2 cm |
| D. | 8 cm |
| Answer» B. 1 cm | |
| 997. |
Cassergain feed is used with a parabolic reflector to |
| A. | increase the gain of the system |
| B. | increase the beamwidth of the system |
| C. | reduce the size of the main reflector |
| D. | allow the feed to be placed at a convenient point |
| Answer» E. | |
| 998. |
For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the value of propagation constant P will be |
| A. | 15.9 radians/km |
| B. | 31.8 radians/km |
| C. | 63.6 radians/km |
| D. | 105.4 radians/km |
| Answer» B. 31.8 radians/km | |
| 999. |
For EM wave propagation in free space, the free space is defined as |
| A. | σ = 0, ε = 1, μ ≠ 1, = 0 |
| B. | σ = 0, ε = 1, μ = 1, = 0, = 0 |
| C. | σ ≠ 0, ε > 1, μ < 1, ≠ 0, = 0 |
| D. | σ = 0, ε = 1, μ = 1, ≠ 0, ≠ 0 |
| Answer» E. | |
| 1000. |
The portion of the atmosphere closest to ground is called ionosphere. |
| A. | 1 |
| B. | |
| Answer» C. | |