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.
| 901. |
What is the characteristic impedance at 10 MHz? |
| A. | 547.7 Ω |
| B. | 54.7 Ω |
| C. | 5.47 Ω |
| D. | .547 Ω |
| Answer» B. 54.7 Œ© | |
| 902. |
MUF is given by |
| A. | fc sec θ |
| B. | fc cos θ |
| C. | |
| Answer» B. fc cos Œ∏ | |
| 903. |
For an ideal antenna, numerical value of directivity must be |
| A. | ‚àû |
| B. | 0 |
| C. | 1 |
| D. | any value |
| Answer» B. 0 | |
| 904. |
The "boundary sphere" between antenna region and free space region appears to "opaque" |
| A. | along the dipole axis |
| B. | along perpendicular direction |
| C. | along the dipole axis as well as perpendicular direction |
| D. | neither along the dipole axis nor along the perpendicular direction |
| Answer» B. along perpendicular direction | |
| 905. |
Skip distance (D) is |
| A. | (D ‚àù f) |
| B. | |
| C. | D = f |
| Answer» B. | |
| 906. |
Radiation intensity in a given direction is the |
| A. | energy radiated per square metre |
| B. | power radiated per square metre |
| C. | power radiated per unit solid angle in that direction |
| D. | none of the above |
| Answer» D. none of the above | |
| 907. |
An isolated sphere in air has a radius equal to meter, its capacitance is |
| A. | pF |
| B. | 1F |
| C. | 4pF |
| D. | 1/4pF |
| Answer» C. 4pF | |
| 908. |
If the height of transmitting and receiving antenna in a LOS system are 49 meter and a 9 meter respectively then the distance up to which communication may be possible is about |
| A. | 40 km |
| B. | 110 km |
| C. | 400 km |
| D. | 1100 km |
| Answer» B. 110 km | |
| 909. |
Poynting vector is associated with which of the following? |
| A. | Power flow in electromagnetic |
| B. | Flux in magnetic field |
| C. | Charge in electrostatic field |
| D. | Current in electrostatic field |
| Answer» B. Flux in magnetic field | |
| 910. |
A parallel polarized wave is incident from air into paraffin having relative permittivity 3, the value of its Brewster angle is |
| A. | 0° |
| B. | 30° |
| C. | 45° |
| D. | 60° |
| Answer» E. | |
| 911. |
In order to receive a vertical polarized wave, the conductor of the dipole should be mounted |
| A. | horizontally |
| B. | vertically |
| C. | at an angle of 45° |
| D. | at an angle of 90° |
| Answer» C. at an angle of 45¬∞ | |
| 912. |
For TE or TM modes of propagation in bounded media, the phase velocity is |
| A. | independent of frequency |
| B. | is a linear function of frequency |
| C. | is a non-linear function of frequency |
| D. | can be frequency dependent or frequency independent on the source |
| Answer» D. can be frequency dependent or frequency independent on the source | |
| 913. |
The electric field on the surface of a perfect conductor is 2V/m. The conductor is immersed in water with ε = 80 ε0. The surface charge density on the conductor is ((ε0 = 10-9/36p)F/m) |
| A. | 0 c/m2 |
| B. | 2 c/m2 |
| C. | 1.8 x 10-11 c/m2 |
| D. | 1.14 x 10-9 c/m2 |
| Answer» E. | |
| 914. |
A Yagi antenna has a driven antenna |
| A. | only |
| B. | with a reflector |
| C. | with one or more directors |
| D. | with a reflector and one or more directors |
| Answer» E. | |
| 915. |
Measurement of radiation resistance by reflection method is suitable for |
| A. | parasitic element antennas |
| B. | low frequency vertical conductor antenna |
| C. | all type of antennas |
| D. | none of the above |
| Answer» B. low frequency vertical conductor antenna | |
| 916. |
Ground wave propagation is useful for |
| A. | microwave |
| B. | medium wave |
| C. | short wave |
| D. | long distance |
| Answer» C. short wave | |
| 917. |
The measure of mismatch between the load and the transmission line is known as |
| A. | directivity |
| B. | Gain |
| C. | standing wave ratio |
| D. | reflection coefficient |
| Answer» E. | |
| 918. |
A 10 GHz signal propagates in a waveguide with a phase velocity of 4 x 108 m/s. If the signal produces standing wave in the guide, then the distance between successive minimal will be |
| A. | 10 mm |
| B. | 20 mm |
| C. | 30 mm |
| D. | 40 mm |
| Answer» C. 30 mm | |
| 919. |
The number of lobes on each side of a 31 resonant antenna will be |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 6 |
| Answer» E. | |
| 920. |
Intrinsic or characteristic impedance of free space has a value of |
| A. | 120 ohm |
| B. | 73 ohm |
| C. | 73 ε ohm |
| D. | 120 ε ohm |
| Answer» E. | |
| 921. |
Due to which of the following reasons a lightning conductor on top of a building is made into a pointed spike? |
| A. | Dust particles may not accumulate |
| B. | Charge per unit area becomes very high for lightening to discharge |
| C. | Rain drops may not collect |
| D. | None of the above |
| Answer» C. Rain drops may not collect | |
| 922. |
Distances near the skip distance should be used for sky-wave propagation |
| A. | to avoid the Faraday effect |
| B. | to avoid tilting |
| C. | to prevent sky-wave and upper ray interference |
| D. | so as to exceed the critical frequency |
| Answer» D. so as to exceed the critical frequency | |
| 923. |
Frequencies in the UHF range propagate by means of |
| A. | space wave |
| B. | surface waves |
| C. | sky waves |
| D. | ground waves |
| Answer» B. surface waves | |
| 924. |
The input impedance of short-circuited line of length l where l < λ/4 |
| A. | inductive |
| B. | capacitive |
| C. | resistive |
| D. | none of the above |
| Answer» B. capacitive | |
| 925. |
An alternating current or voltage is that which |
| A. | changes in magnitude only |
| B. | changes in direction only |
| C. | both (a) and (b) |
| D. | has a random movement of electrons |
| Answer» D. has a random movement of electrons | |
| 926. |
To couple a coaxial line to a parallel to wire line it is best to use a |
| A. | slotted line |
| B. | balun |
| C. | directional coupler |
| D. | quarter wave transformer |
| Answer» C. directional coupler | |
| 927. |
An antenna is synonymous to a |
| A. | generator |
| B. | transformer |
| C. | regulator |
| D. | reflector |
| Answer» C. regulator | |
| 928. |
Gain of an antenna with a circular aperture of diameter 4 meter at frequency of 10 GHz, with directivity 60 |
| A. | 60 |
| B. | 100 |
| C. | 30 |
| D. | 90 |
| Answer» B. 100 | |
| 929. |
The Depth of penetration of EM wave in medium having conductivity σ at a frequency of 1 MHz is 25 cm. The depth of penetration at a frequency of 4 MHz will be |
| A. | 6.25 cm |
| B. | 12.50 cm |
| C. | 50 cm |
| D. | 100 cm |
| Answer» C. 50 cm | |
| 930. |
The capacitance between two spheres, whose separation is very much larger than their radii R, is given approximately as |
| A. | |
| B. | 2pε0R |
| Answer» C. | |
| 931. |
The curve representing Ohm's law is |
| A. | linear |
| B. | a parabola |
| C. | a hyperbola |
| D. | sine function |
| Answer» B. a parabola | |
| 932. |
The electric field of an EM wave propagating in the z direction given by The wave is |
| A. | linearly polarized in z direction |
| B. | elliptically polarized |
| C. | left hand circularly polarized |
| D. | right hand circularly polarized |
| Answer» D. right hand circularly polarized | |
| 933. |
Calculate the directivity of an antenna for θE = 30°, θH = 60 |
| A. | 46 |
| B. | 23 |
| C. | 50 |
| D. | 100 |
| Answer» C. 50 | |
| 934. |
Virtual height of an ionospheric layer is always greater than its actual height. |
| A. | 1 |
| B. | |
| C. | TE only |
| D. | TM only |
| Answer» B. | |
| 935. |
Velocity of the wave when it passes from air into sphere |
| A. | decreases |
| B. | increases |
| C. | same |
| D. | no change |
| Answer» C. same | |
| 936. |
An antenna couple is used due to all of the following reasons except |
| A. | to prevent reradiation of the local oscillator |
| B. | to discriminate against harmonics |
| C. | to make the antenna look resistive |
| D. | to provide the output amplifier with the correct load impedance |
| Answer» B. to discriminate against harmonics | |
| 937. |
A very reliable service has to be established between two points on earth separated by 1000 km. The band that will be used as |
| A. | MF |
| B. | VHF |
| C. | VLF |
| D. | HF |
| Answer» D. HF | |
| 938. |
The critical frequency of 'F' layer is greater than 30 MHz. |
| A. | 1 |
| B. | |
| C. | Z0 is an ac characteristic that is the same for any length of time |
| D. | The characteristic impedance can be measured approximately with a sensitive ohm meter |
| Answer» C. Z0 is an ac characteristic that is the same for any length of time | |
| 939. |
Which one of the following potential does not satisfy Laplace's equations? |
| A. | v = 10 xy |
| B. | v = p cos φ |
| C. | |
| Answer» C. | |
| 940. |
A uniform plane EM wave incident normally on a plane surface of a dielectric material is reflected with a VSWR of 3. What percentage of incident power that is reflected? |
| A. | 0.1 |
| B. | 0.25 |
| C. | 0.5 |
| D. | 0.75 |
| Answer» C. 0.5 | |
| 941. |
A field can be |
| A. | harmonic |
| B. | divergence less |
| C. | solenoidal |
| D. | rotational |
| Answer» E. | |
| 942. |
In figure the voltage distribution on a vertical earthed antenna is represented by |
| A. | curve A |
| B. | curve B |
| C. | curve C |
| D. | curve D |
| Answer» C. curve C | |
| 943. |
In a rectangular waveguide ZTE . ZTM is |
| A. | η02 |
| B. | 1 |
| C. | 1/ η02 |
| D. | η0 |
| Answer» B. 1 | |
| 944. |
In case of static electric field Maxwell's divergence equation states that: |
| A. | ‚àá . = 1/r |
| B. | ∇ . = r/ε0 |
| C. | ∇ . = εr |
| D. | ‚àá . = r |
| Answer» C. ‚àá . = Œµr | |
| 945. |
Good smoothing factor of a coil depends on |
| A. | inductance of the coil |
| B. | terminal voltage |
| C. | cross-sectional area of the wire of the coil |
| D. | property of the wire of the coil |
| Answer» E. | |
| 946. |
In end fire array the principle direction of radiation |
| A. | is perpendicular to the array axis |
| B. | is perpendicular to the array axis and also to the plane containing the array elements |
| C. | coincides with the direction of the array |
| D. | is at 45° to the direction of array axis |
| Answer» D. is at 45¬∞ to the direction of array axis | |
| 947. |
Refraction of electromagnetic waves occurs when they |
| A. | pass through a small slot in a conducting plane |
| B. | pass into a medium of different dielectric constant |
| C. | are polarized at right angles to the direction of propagation |
| D. | encounter a perfectly conduction surface |
| Answer» B. pass into a medium of different dielectric constant | |
| 948. |
A λ/8 section of transmission line is determined of load impedance of (2 - j 5) Ω. If characteristic impedance of line is 10 Ω. Then input impedance of line is |
| A. | 10 Ω |
| B. | (6.9 + j 7.24) Ω |
| C. | (1.75 + j 3.098) Ω |
| D. | (2 - j 5) Ω |
| Answer» D. (2 - j 5) Œ© | |
| 949. |
The velocity of electromagnetic wave in a good conductor is |
| A. | 3 x 108 m/s |
| B. | more than 3 x 108 m/s |
| C. | very low |
| D. | high |
| Answer» D. high | |
| 950. |
A TEM wave incident obliquely on a dielectric boundary with εr1 = 2 and εr2 = 1, the angle of incidence for total reflection is |
| A. | 30° |
| B. | 60° |
| C. | 45° |
| D. | 90° |
| Answer» D. 90¬∞ | |