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.
| 1051. |
300 to 3000 MHz frequency is categorized as |
| A. | MF |
| B. | HF |
| C. | UHF |
| D. | SHF |
| Answer» D. SHF | |
| 1052. |
It is desired to reduce the reflection at an air porcelain by use of 7/4 plate (for Porcelain μ = 40, and εr = 7). The thickness of the polystyrene plate required at 10 GHz will be |
| A. | 5.039 cm |
| B. | 50.39 cm |
| C. | 0.5039 cm |
| D. | 0.05039 cm |
| Answer» D. 0.05039 cm | |
| 1053. |
The radiation resistance of a λ/16 wire dipole in free space will be nearly |
| A. | 1 Ω |
| B. | 3 Ω |
| C. | 13 Ω |
| D. | 30 Ω |
| Answer» C. 13 Œ© | |
| 1054. |
An electric charge Q is placed in a dielectric medium which of the following quantities are independent of the dielectric constant ε of the medium |
| A. | electric potential V and electric field intensity E |
| B. | displacement density D and displacement φ |
| C. | electric field intensity E and displacement φ |
| D. | electric potential V and displacement φ |
| Answer» C. electric field intensity E and displacement œÜ | |
| 1055. |
MF is generally used for |
| A. | telegraphy |
| B. | radio and television links |
| C. | satellite communication |
| D. | broadcasting, navigation |
| Answer» E. | |
| 1056. |
If a plane electromagnetic wave satisfies the equation , the wave propagates in the (at an angle of 45° between the x and z direction) |
| A. | x-direction |
| B. | z-direction |
| C. | y direction |
| D. | xy plane |
| Answer» C. y direction | |
| 1057. |
A transmission line has primary constants R, L, G and C and secondary constant z0 and γ = (a + Jβ). If the line is loss less, then |
| A. | R = 0, G ≠ 0, and a = 0 |
| B. | R = 0, G = a, 0 and β = |r| |
| C. | G = 0, a = β |
| D. | R = 0, G = 0, a = 0, β = |r| |
| Answer» B. R = 0, G = a, 0 and Œ≤ = |r| | |
| 1058. |
Circular polarized waves result when |
| A. | magnitudes are the same |
| B. | phases are the same |
| C. | magnitudes are same and phase difference is 90° |
| D. | magnitudes are same and phase difference is zero |
| Answer» D. magnitudes are same and phase difference is zero | |
| 1059. |
The minimum height of outer atmosphere is |
| A. | 100 km |
| B. | 150 km |
| C. | 200 km |
| D. | 400 km |
| Answer» E. | |
| 1060. |
The attenuation in a waveguide near the cut off frequency is |
| A. | zero |
| B. | low |
| C. | high |
| D. | very high |
| Answer» B. low | |
| 1061. |
End fire array is called a linear resonant dipole array. |
| A. | 1 |
| B. | |
| C. | It changes impedance like current transformer |
| D. | It changes balanced to unbalanced line |
| Answer» B. | |
| 1062. |
A (75 - j 40) W load is connected to a co-axial line of z0 = 75ω at 6 MHz. The load matching on the line can be accomplished by connecting |
| A. | a short circuit stub at the load |
| B. | an inductance at the load |
| C. | a short circuit stub at a specific distance from the load |
| D. | a capacitance at a specific distance from the load |
| Answer» C. a short circuit stub at a specific distance from the load | |
| 1063. |
Television receiver antenna is usually |
| A. | loop type |
| B. | yagi antenna |
| C. | parabolic dishes |
| D. | none of the above |
| Answer» C. parabolic dishes | |
| 1064. |
A transmission line is feeding 1 watt of power to a horn antenna having a gain of 10 dB. The antenna is matched to the transmission line. The total power radiated by the horn antenna into the free space is |
| A. | 10 watts |
| B. | 1 watt |
| C. | 0.1 watt |
| D. | 0.01 watt |
| Answer» B. 1 watt | |
| 1065. |
Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of 1014 Hz in glass. Assume velocity of light is 3 x 108 m/sec in vacuum. |
| A. | 4 μm |
| B. | 3 μm |
| C. | 2 μm |
| D. | 1 μm |
| Answer» D. 1 Œºm | |
| 1066. |
Distilled water at 25°C is characterized by σ = 1.7 x 10-4 mho/m and ε = 78 ε0 at a frequency of 3 GHz. Its loss tangent is (ε = 10-9/36p F/m) |
| A. | 1.3 x 10-5 |
| B. | 1.3 x 10-3 |
| C. | 1.7 x 10-4/78 |
| D. | 1.7 x l0-4/78ε0 |
| Answer» B. 1.3 x 10-3 | |
| 1067. |
For a distortionless line, the parameters are related as |
| A. | R/G = L/C |
| B. | R/L = 1 |
| C. | R/G = C/L |
| D. | RG = LC |
| Answer» B. R/L = 1 | |
| 1068. |
Consider a 300 Ω, quarter wave long at 1 GHz transmission line as shown in figure. It is connected to a 10 V, 50 Ω source at one end is left open circuited at the other end. The magnitude of the voltage at the open circuit end of the line is |
| A. | 10 V |
| B. | 5 V |
| C. | 60 V |
| D. | 60/7 volt |
| Answer» B. 5 V | |
| 1069. |
Which one is correct option? |
| A. | TEM mode exist in free space of infinite boundary |
| B. | TEM mode exist in two conductor pattern system for finite-boundary |
| C. | TEM mode exist in waveguide only |
| D. | Both (a) and (b) |
| Answer» E. | |
| 1070. |
The torque (in mm) acting on a circular current loop of radius 1 mm in the xy plane, connected at the origin and with current 0.1 A, flowing in the sense of increasing in a magnetic field is |
| A. | |
| B. | |
| Answer» C. | |
| 1071. |
Whenever a wave is incident on a perfect conductor then the reflection coefficient is |
| A. | 1 |
| B. | 0 |
| C. | 1 < 180° |
| D. | depend upon η1, η2 |
| Answer» C. 1 < 180¬∞ | |
| 1072. |
Find the noise factor for an antenna at 27°C with equivalent noise temperature 30°K |
| A. | 20 |
| B. | 100 |
| C. | 300 |
| D. | 1.1 |
| Answer» E. | |
| 1073. |
When the phase velocity of an EM wave depends on frequency in any medium, the phenomenon is called |
| A. | scattering |
| B. | polarization |
| C. | absorption |
| D. | dispersion |
| Answer» C. absorption | |
| 1074. |
A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls Calculate group velocity for dominant mode. |
| A. | 1.8 x 108 m/sec |
| B. | 5 x 108 m/sec |
| C. | 3 x 108 m/sec |
| D. | 1.5 x 108 m/sec |
| Answer» B. 5 x 108 m/sec | |
| 1075. |
A material has conductivity of 10-2 mho/m and a relative permittivity of 4. The frequency at which conduction current in the medium is equal to displacement current is |
| A. | 45 MHz |
| B. | 90 MHz |
| C. | 450 MHz |
| D. | 900 MHz |
| Answer» B. 90 MHz | |
| 1076. |
Calculate the wave impedance for TM mode in rectangular waveguide for dominant mode at 3 GHz having |
| A. | (120p) Ω |
| B. | 377 Ω |
| C. | 226 Ω |
| D. | 629 Ω |
| Answer» D. 629 Œ© | |
| 1077. |
The function f(x - vot) represent which of the following? |
| A. | A stationary wave |
| B. | A wave motion in forward direction |
| C. | A wave motion in reverse direction |
| D. | None of the above |
| Answer» C. A wave motion in reverse direction | |
| 1078. |
Which of the following laws of electromagnetic theory is associated with the force experienced by two loops of a wire carrying currents? |
| A. | Maxwell's law |
| B. | Coulomb's law |
| C. | Ampere's law |
| D. | Laplace's law |
| Answer» D. Laplace's law | |
| 1079. |
The input impedance of short-circuited line of length l where λ/4 < l < λ/2, is |
| A. | resistive |
| B. | inductive |
| C. | capacitive |
| D. | none of the above |
| Answer» D. none of the above | |
| 1080. |
A broadside array operating at 100 cm wavelength consist of 4 half-wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be |
| A. | 196 W |
| B. | 73 W |
| C. | 36.5 W |
| D. | 18.25 W |
| Answer» B. 73 W | |
| 1081. |
Consider a loss less antenna with a directive gain of + 6 dB. If 1 mW of power is fed to it the total power radiated by the antenna will be |
| A. | 4 mW |
| B. | 1 mW |
| C. | 7 mW |
| D. | 1/4 mW |
| Answer» B. 1 mW | |
| 1082. |
Tropospheric scatter is used with frequencies in the |
| A. | HF |
| B. | VHF |
| C. | UHF |
| D. | VLF |
| Answer» D. VLF | |
| 1083. |
Consider an arbitrary distribution of conducting bodies in a charge free space according to the uniqueness theorem, which of following are required to be specified in order that the field is uniquely determined everywhere? Total charge on each conductorPotential at each conductor surfacePotential at same of conductor and total charge on the remainderTotal charge as well as potential gradient on each conductor surface Select the correct answer using the codes given below codes |
| A. | 1 and 3 |
| B. | 2 and 4 |
| C. | 1, 2, and 3 |
| D. | 1, 2, 3, 4 |
| Answer» C. 1, 2, and 3 | |
| 1084. |
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 half power beamwidth |
| A. | 4° |
| B. | 2° |
| C. | 10° |
| D. | 15° |
| Answer» C. 10¬∞ | |
| 1085. |
ZL = 200 Ω and it is desired that Zi = 50 Ω The quarter wave transformer should have a characteristic impedance of |
| A. | 100 Ω |
| B. | 40 Ω |
| C. | 10000 Ω |
| D. | 4 Ω |
| Answer» B. 40 Œ© | |