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.
| 851. |
For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the characteristic impedance will be |
| A. | 14 Ω |
| B. | 28 Ω |
| C. | 39 Ω |
| D. | 79 Ω |
| Answer» E. | |
| 852. |
Purpose of antenna is |
| A. | to transmit and receive energy |
| B. | to convert EM into electrical |
| C. | to convert electrical into EM |
| D. | all of the above |
| Answer» E. | |
| 853. |
A rectangular waveguide (2.29 x 1.02) cm operates at a freq. of 11 GHz in TE10 mode. If the maximum potential gradient of the signal is 5 kV/cm, then the maximum power handling capacity of the waveguide will be |
| A. | 31.11 mW |
| B. | 31.11 W |
| C. | 31.11 kW |
| D. | 31.11 MW |
| Answer» D. 31.11 MW | |
| 854. |
Poynting vector signifies which of the following? |
| A. | Power density vector producing electrostatic field |
| B. | Power density vector producing electromagnetic field |
| C. | Current density vector producing electrostatic field |
| D. | Current density vector producing electromagnetic field |
| Answer» C. Current density vector producing electrostatic field | |
| 855. |
For a uniform plane wave of frequency 106 Hz propagating in a good conductor, the field undergoes a change in phase by 2p radius over a distance of 1 meter. The field is attenuated by a factor of 1/e at a distance of |
| A. | m |
| B. | m |
| C. | p m |
| D. | 2p m |
| Answer» B. m | |
| 856. |
T.V. broadcasting based on |
| A. | line of sight communication |
| B. | ionospheric propagation |
| C. | ground wave |
| D. | medium wave |
| Answer» C. ground wave | |
| 857. |
A folded dipole antenna is conveniently connected to |
| A. | shielded line |
| B. | two wire line |
| C. | coaxial line |
| D. | flat ribbon type transmission line |
| Answer» E. | |
| 858. |
Consider isotropic radiator radiating a power of 1 watt. At a distance of 1 metre, the power per unit area with equal |
| A. | 1 watt/m2 |
| B. | 4p watt/m2 |
| C. | 1/4p watt/m2 |
| D. | 2p watt/m2 |
| Answer» D. 2p watt/m2 | |
| 859. |
Curl of gradient A is |
| A. | ‚àá x (‚àáA) = 1 |
| B. | ‚àá x (‚àáA) = ‚àû |
| C. | ‚àá x (‚àáA) = 0 |
| D. | ‚àá x (‚àáA) = - ‚àû |
| Answer» D. ‚àá x (‚àáA) = - ‚àû | |
| 860. |
A long periodic antenna is a |
| A. | frequency independent antenna |
| B. | frequency dependent antenna |
| C. | directional antenna |
| D. | none of the above |
| Answer» B. frequency dependent antenna | |
| 861. |
Antenna commonly used for microwave links are |
| A. | loop antennas |
| B. | log periodic antennas |
| C. | paraboloidal dishes |
| D. | rhombic antennas |
| Answer» D. rhombic antennas | |
| 862. |
Beamwidth (between first nulls) will be for an antenna at 3 MHz with directivity of 100 |
| A. | 140° |
| B. | 70° |
| C. | 210° |
| D. | 60° |
| Answer» B. 70¬∞ | |
| 863. |
For satellite communication, the frequency should be |
| A. | equal to the critical frequency |
| B. | more than the critical frequency |
| C. | less than the critical frequency |
| D. | none of these |
| Answer» C. less than the critical frequency | |
| 864. |
Which of the following is λ/2 length? |
| A. | Marconi |
| B. | Hertz |
| C. | Parabolic |
| D. | Yagi-uda |
| Answer» C. Parabolic | |
| 865. |
An open wire transmission line having a characteristic impedance of 600 ohms is terminated by a resistive load of 900 Ω. The standing wave ratio will be |
| A. | 1.5 |
| B. | 2.5 |
| C. | 3.5 |
| D. | 4.5 |
| Answer» B. 2.5 | |
| 866. |
An electromagnetic wave incidents on a perfect insulator at an angle. If the wave is not entirely parallel polarized, then |
| A. | the reflected wave will be entirely polarized parallel to the plane of incidence |
| B. | there will be no reflection |
| C. | the reflected wave will be entirely polarized perpendicular to the plane of incidence |
| D. | any of the above |
| Answer» D. any of the above | |
| 867. |
The radiation resistance of a resonant long wire antenna of half wavelength (λ/2) is given |
| A. | 73 Ω |
| B. | 120 p |
| C. | 377 Ω |
| D. | 7.3 Ω |
| Answer» B. 120 p | |
| 868. |
The radiation resistance of a rod tubing antenna is |
| A. | 55 Ω to 60 Ω |
| B. | 60 to 100 Ω |
| C. | 0 to 377 Ω |
| D. | 60 to 200 Ω |
| Answer» B. 60 to 100 Œ© | |
| 869. |
For transmission line load matching over a range of frequencies, it is best to use a |
| A. | double stub |
| B. | balun |
| C. | single stub of adjustable position |
| D. | broadband directional coupler |
| Answer» B. balun | |
| 870. |
End fire array has a dipole spacing of λ/2. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 871. |
In E plane metal plate lens antenna |
| A. | travelling wavefronts are retarded |
| B. | travelling wavefront are accelerated |
| C. | travelling wavefront remains unaffected |
| D. | none of the above |
| Answer» C. travelling wavefront remains unaffected | |
| 872. |
When there is rapid attenuation of field inside the conductor, the field current are concentrated close to the surface of the conductor; this phenomenon is called |
| A. | skin effect |
| B. | EM concentration effect |
| C. | Faraday's effect |
| D. | Ohm's effect |
| Answer» B. EM concentration effect | |
| 873. |
Critical frequency of a layer in ionosphere |
| A. | fc = 9 N |
| B. | fc = 81 N2 |
| C. | fc = 81 N |
| Answer» B. fc = 81 N2 | |
| 874. |
Which of the following statement regarding waveguides is incorrect? |
| A. | At waveguide can be coupled to a coaxial cable |
| B. | At frequencies below the cut off value the wave progresses across the waveguide after total reflections |
| C. | Waveguides are usually air filled hollow conducting metallic tubes for transmitting UHF and microwaves |
| D. | Waveguides can handle large power at UHF and microwaves |
| Answer» B. At frequencies below the cut off value the wave progresses across the waveguide after total reflections | |
| 875. |
An antenna is considered to be in free space where its height above the ground is |
| A. | λ |
| B. | 2λ |
| C. | less than 3λ |
| D. | more than 5λ |
| Answer» E. | |
| 876. |
Find the flux crossing the plane surface defined by 0.5 ≤ r ≤ 3.5 m and 0 ≤ z ≤ 3 m. if |
| A. | 0 |
| B. | 255 Wb |
| C. | 6.45 Wb |
| D. | none of the above |
| Answer» B. 255 Wb | |
| 877. |
Frequency band used for radar is generally |
| A. | VLF |
| B. | VHF |
| C. | UHF |
| D. | EHF |
| Answer» D. EHF | |
| 878. |
1 dB is equal to __________ nepier |
| A. | 8.6 |
| B. | 6.8 |
| C. | 8 |
| D. | 0 |
| Answer» B. 6.8 | |
| 879. |
The absorption of radio waves by the atmosphere depends on |
| A. | the polarization of the waves |
| B. | the polarization of the atmosphere |
| C. | frequency of the waves |
| D. | their distance from the transmitter |
| Answer» D. their distance from the transmitter | |
| 880. |
Surface integral of the electric field intensity is |
| A. | differential of volume flux |
| B. | electrical charge |
| C. | net flux emanating from the surface |
| D. | none of the above |
| Answer» D. none of the above | |
| 881. |
__________ acts as a depolarizer in a dry cell. |
| A. | ammonium chloride |
| B. | carbon powder |
| C. | manganese dioxide |
| D. | zinc chloride |
| Answer» D. zinc chloride | |
| 882. |
The attenuation factor a and phase shift factor β for a wave propagated in a good dielectric having are given by |
| A. | a = μ/ε , β = ωμ/ε |
| B. | a = β = μ/ε |
| C. | a = μ/ε , β = ωμ/ε |
| D. | a = β = ωμ/ε |
| Answer» B. a = Œ≤ = Œº/Œµ | |
| 883. |
A (0.75 - j50) ohm load is connected to a coaxial transmission line of Z0 = 75 ohms at a frequency of 10 GHz Which of the following will be the best method of matching? |
| A. | Connecting an inductance at the end |
| B. | Connecting a short circuited stub at the load |
| C. | Connecting a capacitance at some distance from the load |
| D. | Connecting a short circuited stub at some specified distance from the load |
| Answer» E. | |
| 884. |
The important postulate arising out of Maxwell's modification of Ampere's law is |
| A. | a changing magnetic field produces an electric field |
| B. | a changing electric field produces a magnetic field |
| C. | a motional e.m.f. is produced by a coil moving in a magnetic field |
| D. | a steady current produce a magnetic field |
| Answer» C. a motional e.m.f. is produced by a coil moving in a magnetic field | |
| 885. |
Beamwidth of an antenna depends upon |
| A. | shape of radiation pattern |
| B. | dimensions |
| C. | wavelength |
| D. | all of the above |
| Answer» E. | |
| 886. |
Which of the following is a circularly polarized antenna? |
| A. | Rhombic |
| B. | Circular loop |
| C. | Helical |
| D. | Yagi |
| Answer» D. Yagi | |
| 887. |
One volt equals |
| A. | one joule |
| B. | one joule/coulomb |
| C. | one coulomb/joule |
| D. | none of the above |
| Answer» D. none of the above | |
| 888. |
Antenna reciprocity is put to use in |
| A. | radar system |
| B. | commercial broadcast |
| C. | TV broadcast system |
| D. | none of the above |
| Answer» B. commercial broadcast | |
| 889. |
The directive gain of λ/2 resonant wire is 1.64. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 890. |
Microwave signals transmitted towards the sky are |
| A. | strongly absorbed by the ionosphere |
| B. | strongly reflected by the ionosphere |
| C. | transmitted through the ionosphere |
| D. | unable to reach the ionosphere because of strong absorption in the lower atmosphere |
| Answer» D. unable to reach the ionosphere because of strong absorption in the lower atmosphere | |
| 891. |
T.V. antennas are usually |
| A. | Yagi-Uda |
| B. | loops |
| C. | helical |
| D. | parabolic |
| Answer» B. loops | |
| 892. |
Poynting vector is the rate of energy flow having |
| A. | W/m2 |
| B. | W-m |
| C. | kWh/s |
| D. | W/m |
| Answer» B. W-m | |
| 893. |
The cut off wavelength λc for TE20 mode for a standard rectangles waveguide is |
| A. | 2/a |
| B. | 2a |
| C. | a |
| D. | 2a2 |
| Answer» D. 2a2 | |
| 894. |
In figure the current distribution is represented by |
| A. | curve A |
| B. | curve B |
| C. | curve C |
| D. | curve D |
| Answer» D. curve D | |
| 895. |
A short circuited stub is shunt connected to a transmission line as shown in the figure is, if z0 = 500 ohms, the admittance y seen at the function of the stub and the transmission line is |
| A. | (0.01 - j 0.02) mho |
| B. | (0.02 - j 0.01) mho |
| C. | (0.04 - j 0.02) mho |
| D. | (0.02 + j 0) mho |
| Answer» B. (0.02 - j 0.01) mho | |
| 896. |
Antenna is a __________ element |
| A. | passive |
| B. | active |
| C. | resistive |
| D. | capacitive |
| Answer» B. active | |
| 897. |
Which of the following impedance inversion is obtained? |
| A. | Short-circuited stub |
| B. | A quarter wave line |
| C. | Balun transformer |
| D. | A half wave line |
| Answer» C. Balun transformer | |
| 898. |
For an elliptically polarized wave incident on the interface of a dielectric at the Brewster angle the reflected wave will be |
| A. | elliptically polarized |
| B. | linearly polarized |
| C. | right circularly polarized |
| D. | left circularly polarized |
| Answer» B. linearly polarized | |
| 899. |
A dipole antenna was radiating with some excitation in free space radiating a certain amount of the power. If this antenna is immersed in a lake where water is non-dissipative but has a dielectric constant of 81, the radiated power with the same excitation will |
| A. | decrease to finite non-zero value |
| B. | remain the same |
| C. | increase |
| D. | decrease to zero |
| Answer» C. increase | |
| 900. |
A plane electromagnetic wave travels in dielectric medium of relative permittivity 9. Relative to free space, the velocity of propagation in the dielectric is |
| A. | increased by a factor of 9 |
| B. | increased by a factor of 3 |
| C. | unchanged |
| D. | reduced by a factor of 1/3 |
| Answer» E. | |