MCQOPTIONS
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MCQOPTIONS
This section includes 9294 Mcqs, each offering curated multiple-choice questions to sharpen your Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1151. |
Which one is correct? |
| A. | Sky wave propagation (2 to 30 MHz) |
| B. | Space wave propagation (> 30 MHz) |
| C. | Tropospheric propagation (> 300 MHz) |
| D. | All of the above |
| Answer» E. | |
| 1152. |
When a magnetic circuit is compared with an electric circuit, the equivalent of the magnetic flux is |
| A. | the conductivity of the lines |
| B. | the voltage of the source |
| C. | the current in the lines |
| D. | the conductance of the load |
| Answer» D. the conductance of the load | |
| 1153. |
Laplace equation in cylindrical co-ordinates is given by |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/198-272-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/198-272-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/198-272-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/198-272-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/198-272-2.png"> | |
| 1154. |
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 | |
| 1155. |
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 | |
| 1156. |
Which one of the following is correct expression. Where t is torque, B magnetic field, M is the moment |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-311-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-311-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-311-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-311-4.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-311-4.png"> | |
| 1157. |
There is no radiation at right angles to the plane of the array, is end fire array. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 1158. |
Which of the following constitute the loss resistance of an antenna? |
| A. | Dielectric loss |
| B. | Leakage loss in insulation |
| C. | Loss in earth connections |
| D. | All of the above |
| Answer» E. | |
| 1159. |
The M.K.S. unit of magnetic field intensity is |
| A. | ampere |
| B. | ampere/metre |
| C. | volt |
| D. | volt/metre |
| Answer» C. volt | |
| 1160. |
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 | |
| 1161. |
The reflection coefficient is generally a |
| A. | complex number |
| B. | fraction |
| C. | imaginary number |
| D. | none of the above |
| Answer» B. fraction | |
| 1162. |
The advantage of Marconi antenna over the ungrounded antenna is that |
| A. | only one fourth of the height is required as compared to undergrounded antenna |
| B. | one-half of the height is required as compared to undergrounded antenna |
| C. | no capacitance required |
| D. | none of the above |
| Answer» C. no capacitance required | |
| 1163. |
What will be the propagation constant at 10 MHz? |
| A. | 3.4 radians/km |
| B. | 34.4 radians/km |
| C. | 344 radians/km |
| D. | 3440 radians/km |
| Answer» D. 3440 radians/km | |
| 1164. |
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 | |
| 1165. |
In a medium if , and 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 | |
| 1166. |
The directivity of 20 turn helix having a = 12 circumference equal to one wavelength, will be |
| A. | 1.8 dB |
| B. | 6 dB |
| C. | 12 dB |
| D. | 18 dB |
| Answer» E. | |
| 1167. |
The velocity factor of a transmission line |
| A. | mainly depends on the skin effect |
| B. | is always higher for a solid dielectric than for air |
| C. | mainly depends on the dielectric constant of the material used |
| D. | increases the velocity along the transmission line |
| Answer» D. increases the velocity along the transmission line | |
| 1168. |
__________ acts as a depolarizer in a dry cell. |
| A. | ammonium chloride |
| B. | carbon powder |
| C. | manganese dioxide |
| D. | zinc chloride |
| Answer» D. zinc chloride | |
| 1169. |
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. | |
| 1170. |
Tropospheric mode of propagation is used in |
| A. | UHF |
| B. | VLF |
| C. | MF |
| D. | HF |
| Answer» B. VLF | |
| 1171. |
The skip distance is |
| A. | same for each layer |
| B. | independent of frequency |
| C. | independent of the state of ionisation |
| D. | independent of transmitted power |
| Answer» E. | |
| 1172. |
Polystyrene has a relative permittivity of 2.7. If the wave is incident at an angle i of 30 from air into polystyrene, the angle of transmission will be nearly |
| A. | 0.2 |
| B. | 2 |
| C. | 18 |
| D. | 48 |
| Answer» D. 48 | |
| 1173. |
The radiation pattern of helical antenna (axial mode) is represented by |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-484-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-484-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-484-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-484-4.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-484-4.png"> | |
| 1174. |
Antenna aperture efficiency is given by |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-489-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-489-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-489-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-489-4.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-489-4.png"> | |
| 1175. |
An antenna is synonymous to a |
| A. | generator |
| B. | transformer |
| C. | regulator |
| D. | reflector |
| Answer» C. regulator | |
| 1176. |
Alternating current can induce voltage because it has magnetic field which is |
| A. | constant |
| B. | time varying |
| C. | stronger field than D.C. |
| D. | closed loop nature. |
| Answer» C. stronger field than D.C. | |
| 1177. |
Which of the following frequencies cannot be used for reliable beyond-the-horizon terrestrial communications without repeaters? |
| A. | 25 kHz |
| B. | 15 MHz |
| C. | 750 MHz |
| D. | 12 GHz |
| Answer» E. | |
| 1178. |
Beamwidth of an antenna depends upon |
| A. | shape of radiation pattern |
| B. | dimensions |
| C. | wavelength |
| D. | all of the above |
| Answer» E. | |
| 1179. |
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 | |
| 1180. |
Radar antennas are |
| A. | dipoles |
| B. | helical |
| C. | parabolic |
| D. | conical |
| Answer» D. conical | |
| 1181. |
Which of the following are the properties of a medium? |
| A. | Permeability, flux, magnesium |
| B. | Permittivity, permeability, insulation |
| C. | Permeability, resistivity, conductivity |
| D. | Permittivity, permeability, conductivity |
| Answer» E. | |
| 1182. |
In microwave communication, some times, microwave signals reach large distances by following the earth curvature. This phenomenon is called |
| A. | tropospheric scatter |
| B. | faraday effect |
| C. | ionospheric reflection |
| D. | ducting |
| Answer» E. | |
| 1183. |
Given that , if the radiation intensity of an antenna is proportional to sin2 , where is the elevation angle, the antenna directivity will be |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/203-421-2.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/203-421-3.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/203-421-4.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/203-421-5.png"> |
| Answer» E. | |
| 1184. |
Long distance short wave radio broadcasting based on |
| A. | line of sight |
| B. | ionospheric wave |
| C. | ground wave |
| D. | skywave |
| Answer» C. ground wave | |
| 1185. |
The portion of the atmosphere closest to ground is called ionosphere. |
| A. | True |
| B. | False |
| Answer» C. | |
| 1186. |
Many circles are drawn in a Smith chart used for transmission line calculations. The circle shown in the figure represents |
| A. | unit circles |
| B. | constant resistance circles |
| C. | constant reactance circles |
| D. | constant reflection coefficient circles |
| Answer» C. constant reactance circles | |
| 1187. |
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 | |
| 1188. |
A loop antenna is a commonly used for |
| A. | radar |
| B. | direction finding |
| C. | satellite communication |
| D. | all of the above |
| Answer» C. satellite communication | |
| 1189. |
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. | |
| 1190. |
The direction of vectors gives the direction of propagation of electromagnetic waves |
| A. | Vector (E x H) |
| B. | Vector (F x H) |
| C. | Vector E |
| D. | Vector H |
| Answer» B. Vector (F x H) | |
| 1191. |
According to maximum power transfer theorem, the maximum power is absorbed by one network from another network when |
| A. | the impedance of one of the networks is half that of the other |
| B. | the impedance of one is the complex conjugate of the other |
| C. | the impedance of one is equal to that of the other |
| D. | none of the above |
| Answer» C. the impedance of one is equal to that of the other | |
| 1192. |
The static electric field in a conductor is |
| A. | zero |
| B. | unity |
| C. | infinity |
| D. | none of the above |
| Answer» B. unity | |
| 1193. |
The propagation constant of a transmission line is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-491-1.png"> |
| B. | <span class="root">(R + <i>j</i> L)(G + C)</span> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-491-2.png"> |
| D. | none of the above |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/207-491-2.png"> | |
| 1194. |
In a perfect conductor the incident and reflected wave combine to produce |
| A. | a stronger incident wave |
| B. | a stronger reflected wave |
| C. | a standing wave which is not progressing |
| D. | none of the above |
| Answer» D. none of the above | |
| 1195. |
MUF is highest in periods of greatest sunspot activity. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 1196. |
Which antenna is a wideband antenna? |
| A. | Hertz antenna |
| B. | Marconi antenna |
| C. | Folded dipole |
| D. | None of the above |
| Answer» D. None of the above | |
| 1197. |
The radiation pattern of loop antenna is |
| A. | circle |
| B. | semicircle |
| C. | elliptical |
| D. | cardoid or Limacon |
| Answer» E. | |
| 1198. |
Maxwell's curl equation for the static electric field E can be expressed as |
| A. | x E = 0 |
| B. | x E = constant |
| C. | - E = constant |
| D. | . E = 0 |
| Answer» B. x E = constant | |
| 1199. |
The unit of x H is |
| A. | Ampere |
| B. | Ampere/meter |
| C. | Ampere/m |
| D. | <sup>2</sup> |
| E. | Ampere-meter |
| Answer» D. <sup>2</sup> | |
| 1200. |
The relative permittivity of the ionosphere at ratio frequencies is |
| A. | > 1 |
| B. | < 1 |
| C. | = 1 |
| D. | 1 |
| Answer» C. = 1 | |