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.
| 1001. |
A vertical wire of 1 meter length carries a current of 1 A at 10 MHz. The total radiated power is nearly |
| A. | 0.13 W |
| B. | 0.88 W |
| C. | 7.3 W |
| D. | 73 W |
| Answer» E. | |
| 1002. |
Surface impedance at high frequencies is a consideration for |
| A. | ferrites |
| B. | semiconductors |
| C. | good conductors |
| D. | dielectrics |
| Answer» D. dielectrics | |
| 1003. |
The relative permittivity of the ionosphere at ratio frequencies is |
| A. | > 1 |
| B. | < 1 |
| C. | 1 |
| D. | ‚â• 1 |
| Answer» C. 1 | |
| 1004. |
Characteristic impedance of a transmission line is 50 Ω. Input impedance of the open circuited line. Zoc = 100 + J150 Ω. When transmission line is short circuited, then value of the input impedance will be |
| A. | 50 Ω |
| B. | 100 + J150 Ω |
| C. | 7.69 + J11.54Ω |
| D. | 7.69 - J11.54 Ω |
| Answer» E. | |
| 1005. |
Select the correct relation |
| A. | ‚àá(AB) = A ‚àá B + B ‚àá A |
| B. | ‚àá . (AB) = ‚àá A . B + A ‚àá B |
| C. | ‚àá x (AB) = ‚àá A x B + A ‚àá B |
| D. | All of the above |
| Answer» E. | |
| 1006. |
A hertzian dipole has a radiation pattern with |
| A. | a null in the direction of the dipole |
| B. | a null in the plane perpendicular to the dipole |
| C. | a peak in the direction of the dipole |
| D. | none of the above |
| Answer» B. a null in the plane perpendicular to the dipole | |
| 1007. |
A line of characteristic impedance z0 ohms, phase velocity VP = 2 x 108 m/sec and length l = 2 m is terminated by a load impedance zL Ohms. The reflection coefficients at the input end and load end are respectively for a frequency of 50 MHz will be |
| A. | 1 |
| B. | -1 |
| C. | -1 |
| D. | 2 |
| Answer» B. -1 | |
| 1008. |
Short-circuited stubs are preferred to open circuited stubs because the latter are |
| A. | more difficult to make and connect |
| B. | incapable of giving a full range of reactances |
| C. | made of transmission line with a different characteristic impedance |
| D. | liable to radiate |
| Answer» E. | |
| 1009. |
Calculate cut off frequency for dominant mode in rectangular waveguide if dimensions are a = 2, b = 1 cm. |
| A. | 7.5 GHz |
| B. | 1.5 GHz |
| C. | 15 GHz |
| D. | 150 GHz |
| Answer» B. 1.5 GHz | |
| 1010. |
Power gain and directivity related with, Gp power gain, Gd directive gain |
| A. | Gp = η Gd |
| B. | Gd = η Gp |
| C. | |
| Answer» B. Gd = Œ∑ Gp | |
| 1011. |
It is best to use for coupling a coaxial line to a parallel wire transmission line. |
| A. | directional Coupler |
| B. | balun |
| C. | slotted line |
| D. | tee |
| Answer» C. slotted line | |
| 1012. |
The secondary lobes in binomial arrays can be reduced by |
| A. | maintaining spacing between two consecutive radiating sources less than λ/2 |
| B. | maintaining the amplitudes in radiating sources, from outer towards the centre source, proportional to the coefficients of the successive terms of the binomial series |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» D. none of the above | |
| 1013. |
Phase velocity of waves propagating in a hollow metal waveguide is |
| A. | greater than the group velocity |
| B. | less than the velocity of light in free space |
| C. | equal to the velocity of light in free space |
| D. | equal to group velocity |
| Answer» B. less than the velocity of light in free space | |
| 1014. |
The duration of sunspot cycle is |
| A. | 1 year |
| B. | 11 years |
| C. | 55 years |
| D. | 100 years |
| Answer» C. 55 years | |
| 1015. |
A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls calculate the phase velocity for dominant mode. |
| A. | 3 x 108 m/sec |
| B. | 5 x 108 m/sec |
| C. | 1.5 x 108 m/sec |
| D. | 9 x 108 m/sec |
| Answer» C. 1.5 x 108 m/sec | |
| 1016. |
The divergence of the electric field intensity at any point equals |
| A. | 1/4 pε0 times the volume charge density |
| B. | l/ε0 times the volume charge density at that point |
| C. | ε0 times the volume charge density at that point |
| D. | the volume charge density at that point |
| Answer» C. Œµ0 times the volume charge density at that point | |
| 1017. |
A vertical loop antenna, like a horizontal dipole, is vertically polarised. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 1018. |
Which one is not correct for folded dipole antenna? |
| A. | High I/P impedance |
| B. | Low I/P impedance |
| C. | High bandwidth |
| D. | Used as reactance compensation network |
| Answer» C. High bandwidth | |
| 1019. |
The L/C has the dimension of |
| A. | time |
| B. | capacitance |
| C. | velocity |
| D. | resistance |
| Answer» E. | |
| 1020. |
A rectangular metal waveguide filled with a dielectric of relative permittivity εr = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is |
| A. | 2.5 GHz |
| B. | 5 GHz |
| C. | 10 GHz |
| D. | 12.5 GHz |
| Answer» C. 10 GHz | |
| 1021. |
The phase angle corresponding to λ/4 in a standing-wave pattern is |
| A. | 30° |
| B. | 90° |
| C. | 135° |
| D. | 180° |
| Answer» C. 135¬∞ | |
| 1022. |
A plane EM wave is travelling in an unbound loss less dielectric having μy = 1 and εy = 4, the time average Poynting vector of the wave is 5 W/m3 . The phase velocity vp (assuming velocity of light as 3 x 108 m/sec) is |
| A. | 1.5 x 108 m/sec |
| B. | 3 x 108 m/sec |
| C. | 2.5 x 108 m/sec |
| D. | 0.5 x 108 m/sec |
| Answer» B. 3 x 108 m/sec | |
| 1023. |
In a line VSWR of a load is 6 dB. The reflection coefficient will be |
| A. | 0.033 |
| B. | 0.33 |
| C. | 0.66 |
| D. | 3.3 |
| Answer» D. 3.3 | |
| 1024. |
When microwave signals follow the curvature of the earth, this is known as |
| A. | the Faraday effect |
| B. | ducting |
| C. | tropospheric scatter |
| D. | ionospheric reflection |
| Answer» C. tropospheric scatter | |
| 1025. |
Calculate wave impedance for TE mode |
| A. | (377)Ω |
| B. | 226 Ω |
| C. | ‚àû |
| D. | 629 Ω |
| Answer» E. | |
| 1026. |
Which of the following is abnormal variation in ionosphere? |
| A. | Diurnal variation |
| B. | Seasonal variation |
| C. | Ionospheric storms |
| D. | None of the above |
| Answer» D. None of the above | |
| 1027. |
Given figure shows a 90° sector of spherical reflector with vertex 'V', centre of curvature 'C' and equal distances VD, DF, FE and EC. When a beam of EM wave is incident parallel to the axis, all the energy will pass through the region |
| A. | VD |
| B. | DF |
| C. | EF |
| D. | EC |
| Answer» E. | |
| 1028. |
In a 100 turn coil, if the flux through each turn is (t3 - 2t)mWb, the magnitude of the induced emf in the coil at a time of 4 sec is |
| A. | 46 mV |
| B. | 56 mV |
| C. | 4.6 V |
| D. | 5.6 V |
| Answer» D. 5.6 V | |
| 1029. |
A hollow rectangular waveguide has dimensions a = 2b. Calculate the amount of attenuation, if the frequency is 3 GHz, and b = 1 cm. |
| A. | 49 |
| B. | 47.33 |
| C. | 50.33 |
| D. | 50 |
| Answer» C. 50.33 | |
| 1030. |
The discone antenna is |
| A. | a useful direction finding antenna |
| B. | used as a radar receiving antenna |
| C. | useful as a UHF receiving antenna |
| D. | circular polarized like other circularly antenna |
| Answer» D. circular polarized like other circularly antenna | |
| 1031. |
In order to receive a vertically polarized wave, the conductor of the dipole should be mounted |
| A. | horizontally |
| B. | vertically |
| C. | at an angle of 45° |
| D. | none of the above |
| Answer» C. at an angle of 45¬∞ | |
| 1032. |
A ship-to-ship communication system is plagued by fading. The best solution seems to be the use of |
| A. | space diversity |
| B. | frequency diversity |
| C. | a broad band antenna |
| D. | a more directional antenna |
| Answer» C. a broad band antenna | |
| 1033. |
Long distance short-wave radio broadcasting uses |
| A. | ground wave |
| B. | ionospheric wave |
| C. | direct wave |
| D. | any of the above |
| Answer» C. direct wave | |
| 1034. |
Microwave signals follow the curvature of the earth and the phenomenon is known as |
| A. | tropospheric scatter |
| B. | duct propagation |
| C. | Faraday effect |
| D. | none of the above |
| Answer» C. Faraday effect | |
| 1035. |
Maximum effective aperture of a antenna is |
| A. | 1.3 λ2 |
| B. | 0.13 λ2 |
| C. | 13 λ2 |
| D. | 3.1 λ2 |
| Answer» C. 13 Œª2 | |
| 1036. |
A rectangular waveguide measures 3 x 4.5 cm internally and has a 10 GHz signal propagated in it. Calculate the wave impedance for dominant mode. |
| A. | 130 p |
| B. | 1.3 p |
| C. | 120 p |
| D. | 0.5 |
| Answer» C. 120 p | |
| 1037. |
Which of the following antenna is best guided by a waveguide? |
| A. | Biconical |
| B. | Horn |
| C. | Helical |
| D. | Dish |
| Answer» C. Helical | |
| 1038. |
A uniform plane wave travelling in air is incident on the plane boundary between air and another dielectric medium with εr = 4. The reflection coefficient for the normal incidence is |
| A. | zero |
| B. | 0.5 ∠180° |
| C. | 0.33 ∠0° |
| D. | 0.33 ∠180° |
| Answer» E. | |
| 1039. |
Permeance is analogue to |
| A. | reluctance |
| B. | conductance |
| C. | capacitance |
| D. | resistance |
| Answer» C. capacitance | |
| 1040. |
During day time ionosphere consist of |
| A. | D, E, F2 layers |
| B. | D, E, F layers |
| C. | D, E, F1, F2 layer |
| D. | none |
| Answer» D. none | |
| 1041. |
The displacement flux density at a point on the surface of a perfect conductor is = 2(ax - 3 az)c/m2 pointing away from the surface. The charge density at that point c/m2 will be |
| A. | 2 |
| B. | -2 |
| C. | 4 |
| D. | -4 |
| Answer» D. -4 | |
| 1042. |
An end fire array consisting of several half-wave lengths of directive gain 40, then find the width of major lobe |
| A. | 60 |
| B. | 50 |
| C. | 51.25 |
| D. | None of the above |
| Answer» D. None of the above | |
| 1043. |
Maxwell's divergence equation for the magnetic field is given as |
| A. | ‚àá . B = 0 |
| B. | ‚àá2 . B = 0 |
| C. | ‚àá . B = constant |
| D. | ‚àá2 . B = constant |
| Answer» B. ‚àá2 . B = 0 | |
| 1044. |
What does the expression represent? |
| A. | Electric Energy density |
| B. | Magnetic Energy density |
| C. | Power density |
| D. | Radiation Resistance |
| Answer» C. Power density | |
| 1045. |
‚àá . = 0 is frequently known as |
| A. | continuity equation for steady currents |
| B. | Laplace equation |
| C. | Poisson's equation |
| D. | none of the above |
| Answer» B. Laplace equation | |
| 1046. |
The shunt admittance of a transmission line is given by |
| A. | γ = R + jωL |
| B. | γ = R - jωL |
| C. | γ = G + jωC |
| D. | γ = jωGC |
| Answer» D. Œ≥ = jœâGC | |
| 1047. |
Tropospheric mode of propagation is used in |
| A. | UHF |
| B. | VLF |
| C. | MF |
| D. | HF |
| Answer» B. VLF | |
| 1048. |
Calculate the directivity of a given linear end fire, uniform array of 20 element, each separated by λ/3 |
| A. | 100 |
| B. | 10 |
| C. | 26.66 |
| D. | 30 |
| Answer» D. 30 | |
| 1049. |
In a conductor which of the following relations hold good? |
| A. | ‚àá x D = r |
| B. | ‚àá . D = r |
| C. | ‚àá x D = 0 |
| D. | ‚àá . D = 0 |
| Answer» D. ‚àá . D = 0 | |
| 1050. |
For F1 layer the maximum ionic density is 2.3 x 104 electrons per cc. The critical frequency for this layer will be |
| A. | 1.36 MHz |
| B. | 13.6 MHz |
| C. | 136 MHz |
| D. | 1360 MHz |
| Answer» C. 136 MHz | |