MCQOPTIONS
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MCQOPTIONS
This section includes 47 Mcqs, each offering curated multiple-choice questions to sharpen your Electromagnetic Theory knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Antenna is an electrical device which converts |
| A. | Electrical signals to electromagnetic waves |
| B. | Electromagnetic waves to Electrical signals |
| C. | Both a & b |
| D. | None of the above |
| Answer» D. None of the above | |
| 2. |
An antenna is a device which |
| A. | Converts electric power into radio waves or vice versa |
| B. | Converts a sound wave to a magnetic signal |
| C. | Converts a sound wave of one wavelength to other |
| D. | Converts an AC to DC |
| Answer» B. Converts a sound wave to a magnetic signal | |
| 3. |
Match the following Lists:List-I List-II(a) Directive Gain(i) \(\frac{{radiated\;power}}{{total\;input\;power}}\)(b) Directivity(ii) \(\frac{{{\lambda ^2}}}{{4\pi }}.D\)(c) Power Gain(iii) \(\frac{{4\pi \psi }}{{{P_{\left( {radiated} \right)}}}}\)(d) Effective Area(iv) \(10{\log _{10}}{\left( {{g_d}} \right)_{max}}\) Correct codes are:Code: |
| A. | a-i, b-ii, c-iv, d-iii |
| B. | a-iii, b-iv, c-i, d-ii |
| C. | a-iv, b-iii, c-ii, d-i |
| D. | a-ii, b-iii, c-iv, d-i |
| Answer» C. a-iv, b-iii, c-ii, d-i | |
| 4. |
If a dipole Antenna has a radiation resistance of 73 ohm, The loss resistance of 7 ohm and the power gain is 16. Then the directivity is: |
| A. | 14.6 |
| B. | 24.7 |
| C. | 40 |
| D. | 17.53 |
| Answer» E. | |
| 5. |
If the antenna diameter in a radar system is increased by a factor of 4, the maximum range will be increased by a factor of |
| A. | 2 |
| B. | 4 |
| C. | 8 |
| D. | 16 |
| Answer» B. 4 | |
| 6. |
Antenna gain is: |
| A. | Product of directivity gain and antenna efficiency |
| B. | Directive gain / Antenna efficiency |
| C. | Antenna efficiency / Directive gain |
| D. | Equal to directive gain |
| Answer» B. Directive gain / Antenna efficiency | |
| 7. |
Evaluate radiation resistance of an Hertzian dipole for the radiating element, having L = 1 m at f = 30 MHz with uniform current distribution. |
| A. | 9 |
| B. | 10 |
| C. | 5 |
| D. | 8 |
| Answer» E. | |
| 8. |
A microwave communication link employs two antennas for transmission and reception elevated at 200 m and 80 m, respectively. Considering obliqueness of the Earth, the maximum possible link distance is |
| A. | 46 km |
| B. | 64 km |
| C. | 96 km |
| D. | 102 km |
| Answer» D. 102 km | |
| 9. |
In tropospheric scatter links, it is necessary to have __________ |
| A. | high transmitting power |
| B. | parabolic antenna reflectors |
| C. | low noise receivers |
| D. | all of these |
| Answer» E. | |
| 10. |
Directions: Each of the next items consist of two statements, one labeled as the ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the codes given below:Statement (I): an antenna of length \(\frac{\lambda }{2}\) will have a radiation pattern of two lobes.Statement (II): An antenna of length \(\frac{{3\lambda }}{2}\) will have a radiation pattern of two lobes and two minor lobes.Codes: |
| A. | Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I). |
| B. | Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I). |
| C. | Statement (I) is true but Statement (II) is false. |
| D. | Statement (I) is false but Statement (II) is true. |
| Answer» D. Statement (I) is false but Statement (II) is true. | |
| 11. |
Antennas used in Microwave Communication are |
| A. | Parabolic antennas |
| B. | Dipole antennas |
| C. | Omni direction Antennas |
| D. | All of these |
| Answer» B. Dipole antennas | |
| 12. |
If ‘Z’ is the impedance of a simple dipole, the impedance of ‘n’ fold dipole is given by: |
| A. | n Z |
| B. | n2 Z |
| C. | Z/n |
| D. | Z/n2 |
| Answer» C. Z/n | |
| 13. |
Match the following lists in terms of directivity of the antennas:List - IList - IIa) Short dipolei) 1.64b) \(\frac{\lambda }{4}\) Monopoleii) 6.8c) \(\frac{\lambda }{2}\) Monopoleiii) 3.28d) \(\frac{\lambda }{2}\) dipoleiv) 1.5 Correct code are: |
| A. | (a) – (i), (b) – (ii), (c) – (iii), (d) – (iv) |
| B. | (a) – (iv), (b) – (ii), (c) – (i), (d) – (iii) |
| C. | (a) – (iv), (b) – (iii), (c) – (ii), (d) – (i) |
| D. | (a) – (iii), (b) – (iv), (c) – (ii), (d) – (i) |
| Answer» D. (a) – (iii), (b) – (iv), (c) – (ii), (d) – (i) | |
| 14. |
An antenna is desired to operate on a frequency of 40 MHz whose quality factor is 50. The bandwidth of the antenna is |
| A. | 20 kHz |
| B. | 80 kHz |
| C. | 800 kHz |
| D. | 8 kHz |
| Answer» D. 8 kHz | |
| 15. |
A device that makes possible the use of the same antenna for transmission and reception both |
| A. | the duplexer |
| B. | the magic-tee |
| C. | the crystal diode |
| D. | none of the above |
| Answer» B. the magic-tee | |
| 16. |
A communication link operating at 3 GHz has a 22.5 W transmitter connected to an antenna of 2.5 m2 effective aperture. The receiving antenna has an effective aperture of 0.5 m2 and is located at 15 km line-of-sight distance from the transmitting antenna (assume lossless, matched antennas). The power delivered to the receiver is: |
| A. | 12.5 μW |
| B. | 125 μW |
| C. | 12.5 mW |
| D. | 125 mW |
| Answer» B. 125 μW | |
| 17. |
An antenna with radiation resistance 330 Ω operates at 1 GHz and with a current of 4 A. Find the radiated power. |
| A. | 4800 W |
| B. | 5280 W |
| C. | 6100 W |
| D. | 6200 W |
| Answer» C. 6100 W | |
| 18. |
An antenna radiates isotropically over a half-space above a perfectly conducting flat ground plane. If E = 50 mV m–1 rms at a distance of 1 km and the antenna terminal current I = 3.5 A, the radiation resistance will be |
| A. | 3.4 Ω |
| B. | 4.3 Ω |
| C. | 5.2 Ω |
| D. | 6.1 Ω |
| Answer» B. 4.3 Ω | |
| 19. |
Patch is a: |
| A. | High gain wideband antenna |
| B. | High gain narrowband antenna |
| C. | Low gain narrowband antenna |
| D. | Low gain wideband antenna |
| Answer» D. Low gain wideband antenna | |
| 20. |
Consider the following applications in respect of a square corner reflector:1. Radio astronomy2. Point-to-point communicantion3. TV broadcastWhich of the above applications is/are correct? |
| A. | 1 only |
| B. | 1 and 2 only |
| C. | 2 and 3 only |
| D. | 1, 2 and 3 |
| Answer» E. | |
| 21. |
A single-mode fiber with a radius of 4.2 μm, with core-refractive index = 1.48 and that of cladding = 1.475, the cut-off wavelength is given by: |
| A. | λc = 1334 nm |
| B. | λc = 1525 nm |
| C. | λc = 990 nm |
| D. | λc = 1290 nm |
| Answer» B. λc = 1525 nm | |
| 22. |
A receiving antenna with a gain of 40 dB looks at a sky with a noise temperature of 15 K. The loss between the antenna and LNA input due to the feed horn is 0.4 dB, and the LNA has a noise temperature of 40 K. The \(\frac{G}{T}\) value is |
| A. | 11.2 dB/K |
| B. | 13.4 dB/K |
| C. | 20.6 dB/K |
| D. | 39.0 dB/K |
| Answer» D. 39.0 dB/K | |
| 23. |
In case of linear arrays of 'n' isotropic point sources of equal amplitude and spacings. The expression for total electric field at a large distance in the direction 'θ' is given by |
| A. | \(E=\dfrac{1+e^{jn\Psi}}{1-e^{j\Psi}}\) |
| B. | \(E=\dfrac{1+e^{jn\Psi}}{1+e^{j\Psi}}\) |
| C. | \(E=\dfrac{1-e^{j\Psi}}{1+e^{nj\Psi}}\) |
| D. | \(E=\dfrac{1-e^{jn\Psi}}{1-e^{j\Psi}}\) |
| Answer» E. | |
| 24. |
A multimode graded-index fiber exhibits a total pulse broadening of 0.1 μs over a distance of 15 km. The following data is estimated by using the concept that there is no inter-symbol interference:a) The maximum possible Bandwidth is 5 MHzb) The dispersion per unit length is 6.67 ns/kmc) The maximum possible B.W. is 10 MHzd) The dispersion/unit length is 3.37 ns/kmWhich is the correct option? |
| A. | (a) and (d) |
| B. | (b) and (c) |
| C. | (c) and (d) |
| D. | (a) and (b) |
| Answer» E. | |
| 25. |
A mobile antenna receives two copies of the signal transmitted by the base station. The first copy is the line-of-sight component and the other is a reflected component which is 20 dB weaker in terms of Power than the LoS component and delayed by 100 ns. If the signal is sufficiently wideband, causing constructive and destructive interference at different frequency points within the signal bandwidth. What will be the ratio of maximum to minimum signal level variation across bandwidth and what will be the frequency separation between two consecutive maxima or minima? |
| A. | 101/99, 10 MHz |
| B. | 121/81, 10 MHz |
| C. | 101/99, 5 MHz |
| D. | 121/81, 5 MHz |
| Answer» C. 101/99, 5 MHz | |
| 26. |
For efficient radiation and reception, the transmitting and receiving antennas would have to have lengths comparable to ______ |
| A. | equal wavelength |
| B. | half wavelength |
| C. | quarter wavelength |
| D. | 3/4th wavelength |
| Answer» D. 3/4th wavelength | |
| 27. |
Radiation from a helical antenna is |
| A. | plane polarised |
| B. | partially plane polarised |
| C. | circularly polarised |
| D. | elliptically polarised |
| Answer» D. elliptically polarised | |
| 28. |
A half-wavelength antenna has radiation resistance equal to |
| A. | 700 Ω |
| B. | 300 Ω |
| C. | 73 Ω |
| D. | 47 Ω |
| Answer» D. 47 Ω | |
| 29. |
Find the effective area of a half-wave dipole at 1 GHz. |
| A. | 0.0118 m2 |
| B. | 0.0414 m2 |
| C. | 0.0318 m2 |
| D. | 0.0218 m2 |
| Answer» B. 0.0414 m2 | |
| 30. |
If aperture efficiency is 70%, the directivity D of a parabolic dish antenna as a function of its radius is |
| A. | \(20{\left( {\frac{r}{\lambda }} \right)^2}\) |
| B. | \(28{\left( {\frac{r}{\lambda }} \right)^2}\) |
| C. | \(36{\left( {\frac{r}{\lambda }} \right)^2}\) |
| D. | \(44{\left( {\frac{r}{\lambda }} \right)^2}\) |
| Answer» C. \(36{\left( {\frac{r}{\lambda }} \right)^2}\) | |
| 31. |
If an antenna has a main beam with both half-power beamwidths equal to 20°, its directivity (D) is nearly: |
| A. | 90.6 |
| B. | 102.5 |
| C. | 205 |
| D. | 226 |
| Answer» C. 205 | |
| 32. |
For the microwave antenna |
| A. | Shape only depends on the frequency range used |
| B. | Size only depends on the frequency range used |
| C. | Neither shape nor size depends on the frequency range used |
| D. | Both shape and size depends on the frequency range used |
| Answer» E. | |
| 33. |
Assertion (A): The diameter of SMF is selected in such a way that single fundamental ray travels straight along the axis of the core of the fiber.Reason (R): The diameter of core of SMF is more than 10 μm and outer diameter is less than 125 μm. |
| A. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| B. | Both (A) and (R) are true, but (R) is not the correct explanation of (A). |
| C. | (A) is true, but (R) is false. |
| D. | (A) is false, but (R) is true. |
| Answer» D. (A) is false, but (R) is true. | |
| 34. |
A straight dipole radiator fed in the center will produce maximum radiation at1. The plane parallel to its axis2. The plane normal to its axis3. Extreme endsWhich of the above statements is/are correct/ |
| A. | 1 only |
| B. | 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» C. 1 and 3 only | |
| 35. |
Match column A with column B. Column A Column B 1. Point electromagnetic source P. Highly directional 2. Dish antenna Q. End fire 3. Yagi-Uda antenna R. Isotropic |
| A. | 1 – P, 2 – Q, 3 - R |
| B. | 1 – R, 2 – P, 3 - Q |
| C. | 1 – Q, 2 – P, 3 - R |
| D. | 1 – R, 2 – Q, 3 - P |
| Answer» C. 1 – Q, 2 – P, 3 - R | |
| 36. |
Given below are two statements. One is labeled as Assertion (A) and the other is labeled as reason (R).Assertion (A): Optical fibers have higher bandwidth as compared to conventional copper cables.Reason (R): The information-carrying capacity of optical fiber is limited by Rayleigh scattering loss.Choose the correct option. |
| A. | Both (A) and (R) are true and (R) is the correct explanation of (A) |
| B. | Both (A) and (R) are true and (R) is not the correct explanation of (A) |
| C. | (A) is true but (R) is false |
| D. | (A) is false but (R) is true |
| Answer» C. (A) is true but (R) is false | |
| 37. |
Indicate the antenna that is not wideband |
| A. | Discone |
| B. | Folded dipole |
| C. | Helical |
| D. | Marconi |
| Answer» E. | |
| 38. |
Consider the following statements with reference to dipole arrays:1. In broadside array, all the dipoles are fed in the same phase from the same source.2. In the end-fire array, the magnitude of the current in each element is the same and there is no phase difference between these currents.Which of the above statements is/are correct? |
| A. | 1 only |
| B. | 2 only |
| C. | Both 1 and 2 |
| D. | Neither 1 nor 2 |
| Answer» B. 2 only | |
| 39. |
Helical antennas are often used for satellite tracking in VHF range because of: |
| A. | Troposcatter |
| B. | Super - refraction |
| C. | Ionospheric refraction |
| D. | Faraday effect |
| Answer» E. | |
| 40. |
An antenna with input resistance of 73 Ω is connected to a 50 Ω line. If the losses are ignored, then its efficiency is nearly |
| A. | 0.19 |
| B. | 0.81 |
| C. | 0.97 |
| D. | 1.19 |
| Answer» C. 0.97 | |
| 41. |
For an isotropic radiator, the radiation intensity for a given total radiated power of (P) is given by |
| A. | P/2π |
| B. | P/4π |
| C. | 4πP |
| D. | None of the above |
| Answer» C. 4πP | |
| 42. |
A microwave antenna with the absorbing cross-section area (A) and the power flux density (S) in the incident wave is employed as an absorber. The absorbed power (P) of the antenna is |
| A. | \(\frac{A}{S}\) |
| B. | \(\frac{S}{A}\) |
| C. | SA |
| D. | \(\frac{{S + 1}}{{A - 1}}\) |
| Answer» D. \(\frac{{S + 1}}{{A - 1}}\) | |
| 43. |
A company operating taxicabs communicates from its central office with the help of an antenna at the top of a 16m tower. The antenna on the taxicabs is 1.44 m above the ground. The communication distance between the central office and a taxicab cannot exceed |
| A. | 18.6 km |
| B. | 24.0 km |
| C. | 50.0 km |
| D. | 62.3 km |
| Answer» B. 24.0 km | |
| 44. |
For a 4-element broadside antenna array, Ψ equals |
| A. | sin ϕ |
| B. | π cos ϕ |
| C. | \(\frac{{\cot \phi }}{{\sqrt 2 \;\pi }}\) |
| D. | π sin ϕ |
| Answer» C. \(\frac{{\cot \phi }}{{\sqrt 2 \;\pi }}\) | |
| 45. |
A Yagi-uda array does not have |
| A. | high gain |
| B. | high band width |
| C. | parasitic reflector |
| D. | parasitic director |
| Answer» C. parasitic reflector | |
| 46. |
A transmitting antenna of 100 m height radiates 40 kW at a frequency of 100 MHz uniformly in the Azimuth plane. If the height of the receiver antenna is 16 m, the value of Line of sight distance is given by : |
| A. | 25 km |
| B. | 57.68 km |
| C. | 27.68 km |
| D. | 114 km |
| Answer» C. 27.68 km | |
| 47. |
A system has a receiver noise reactance of 50 Ω. It is connected to an antenna with an output resistance of 50 Ω. The noise figure of the system is: |
| A. | 1 |
| B. | 2 |
| C. | 50 |
| D. | 101 |
| Answer» C. 50 | |