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.
| 1401. |
The attenuation in a waveguide near the cut off frequency is |
| A. | zero |
| B. | low |
| C. | high |
| D. | very high |
| Answer» B. low | |
| 1402. |
T.V. antennas are usually |
| A. | Yagi-Uda |
| B. | loops |
| C. | helical |
| D. | parabolic |
| Answer» B. loops | |
| 1403. |
The I/P impedance of a long short circuited section of a loss less transmission line is |
| A. | zero |
| B. | inductive |
| C. | capacitance |
| D. | infinite |
| Answer» C. capacitance | |
| 1404. |
For frequencies upto 1650 kHz __________ antenna is used |
| A. | yagi |
| B. | grounded |
| C. | turnstile |
| D. | marconi |
| Answer» B. grounded | |
| 1405. |
Due to which of the following reasons, the ground wave eventually disappears, as one moves away from the transmitter? |
| A. | Tilting |
| B. | Loss of line-of-eight conditions |
| C. | Interference from the sky wave |
| D. | Maximum single hop distance limitation |
| Answer» B. Loss of line-of-eight conditions | |
| 1406. |
A loop antenna may be of |
| A. | square on triangular shape |
| B. | hexagonal shape |
| C. | circular shape |
| D. | any of the above |
| Answer» E. | |
| 1407. |
Velocity of the wave when it passes from air into sphere |
| A. | decreases |
| B. | increases |
| C. | same |
| D. | no change |
| Answer» C. same | |
| 1408. |
The ratio of the directivity of an end fire antenna to that of a broadside antenna is |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 5 |
| Answer» B. 3 | |
| 1409. |
The absorption of radio waves by atmosphere depends on |
| A. | their frequency |
| B. | their distance from the transmitter |
| C. | the polarization of atmosphere |
| D. | the polarization of the waves |
| Answer» B. their distance from the transmitter | |
| 1410. |
The directive gain of an antenna is given by |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/209-541-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/209-541-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/209-541-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/209-541-4.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/209-541-4.png"> | |
| 1411. |
For transmission-line matching over range of frequencies, it is best to use a |
| A. | single stub of adjustable position |
| B. | double stub |
| C. | broadband directional coupler |
| D. | balun |
| Answer» C. broadband directional coupler | |
| 1412. |
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. | <span class="root">-1</span> |
| D. | 2 |
| Answer» B. - 1 | |
| 1413. |
When a particular mode is excited in a waveguide, these appears an extra electric components in the direction of propagation. The resulting mode is |
| A. | Transverse electric |
| B. | Transverse magnetic |
| C. | Longitudinal |
| D. | Transverse Electromagnetic |
| Answer» C. Longitudinal | |
| 1414. |
An antenna has a gain of 44 dB. Assuming that the main beam of the antenna is circular in cross-section the beamwidth will be |
| A. | 0.4456 |
| B. | 1.4456 |
| C. | 2.4456 |
| D. | 3.4456 |
| Answer» D. 3.4456 | |
| 1415. |
In cellphone communication base antennas are connected to other base antennas in |
| A. | line of sight communication |
| B. | ionospheric propagation |
| C. | ground wave propagation |
| D. | medium wave propagation |
| Answer» B. ionospheric propagation | |
| 1416. |
. = 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 | |
| 1417. |
A rhombic antenna is a |
| A. | resonant antenna |
| B. | non-resonant antenna |
| C. | coupled antenna |
| D. | none of the above |
| Answer» C. coupled antenna | |
| 1418. |
Diffraction of electromagnetic waves |
| A. | may occur around the edge of a sharp obstacle |
| B. | is caused by reflections from the ground |
| C. | arises only with the spherical wave fronts |
| D. | will occur when the waves pass through a large slot |
| Answer» B. is caused by reflections from the ground | |
| 1419. |
Microwave signals transmitted towards the sky are |
| A. | strongly absorbed by the ionosphere |
| B. | strongly reflected by the ionosphere |
| C. | transmitted through the ionosphere |
| D. | unable to reach the ionosphere because of strong absorption in the lower atmosphere |
| Answer» D. unable to reach the ionosphere because of strong absorption in the lower atmosphere | |
| 1420. |
Radiation intensity does not depend upon |
| A. | the antenna direction |
| B. | antenna width |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» C. both (a) and (b) | |
| 1421. |
Voltage standing wave pattern in a loss less transmission line with characteristic impedance 50 &ohm; and a resistive load is shown in the figure. Reflection coefficient is given by |
| A. | -0.6 |
| B. | -1 |
| C. | 0.6 |
| D. | 0 |
| Answer» D. 0 | |
| 1422. |
Which of the following wave remains unaffected during day and night? |
| A. | Tropospheric wave |
| B. | Sky wave |
| C. | Ground wave |
| D. | None of the above |
| Answer» D. None of the above | |
| 1423. |
The phase velocity of an EM wave propagating in a hollow metallic rectangular waveguide in the TE10 mode is |
| A. | equal to its group velocity |
| B. | less than the velocity of light in free space |
| C. | equal to the velocity of light in free space |
| D. | greater than the velocity of light in free space |
| Answer» E. | |
| 1424. |
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 | |
| 1425. |
Which of the following waves do not exist in waveguides? |
| A. | TE waves |
| B. | TM waves |
| C. | TE and TM waves |
| D. | TEM waves |
| Answer» D. TEM waves | |
| 1426. |
If short-circuited and open circuited impedances are 5 ohms and 20 ohms, then characteristic impedance is |
| A. | 1 ohms |
| B. | 10 ohms |
| C. | 25 ohms |
| D. | 100 ohms |
| Answer» C. 25 ohms | |
| 1427. |
A microwave link uses only line-of-sight propagation. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 1428. |
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. | |
| 1429. |
Ionospheric storm causes an abnormal decrease in the critical frequency. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 1430. |
Which of the following is best excited from a waveguide? |
| A. | Discone |
| B. | Helical |
| C. | Biconical |
| D. | Horn |
| Answer» E. | |
| 1431. |
A medium is said to be isotropic when |
| A. | = 0 |
| B. | = |
| C. | = |
| D. | is scalar constant |
| Answer» E. | |
| 1432. |
The frequencies in ultra high frequency range are propagated by means of __________ waves |
| A. | surface |
| B. | ground |
| C. | sky |
| D. | space |
| Answer» E. | |
| 1433. |
The effective refraction index of the ionosphere for radio wave is |
| A. | more than unity |
| B. | less than unity |
| C. | equal to unity |
| D. | either more or less than unity depending on the electron concentration |
| Answer» C. equal to unity | |
| 1434. |
For space propagation, what will be the electric field strength at receiving antenna |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/201-338-1.png"> |
| B. | <span class="root"> 30 W<sub>T</sub>G<sub>T</sub></span> |
| C. | 173 |
| D. | <span class="root">W<sub>T</sub></span> |
| E. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/201-338-2.png"> |
| Answer» B. <span class="root"> 30 W<sub>T</sub>G<sub>T</sub></span> | |
| 1435. |
The radiation resistance of a resonant long wire antenna of half wavelength ( /2) is given |
| A. | 73 Ω |
| B. | 120 |
| C. | <span class="symbol">p</span> |
| D. | 377 Ω |
| E. | 7.3 Ω |
| Answer» B. 120 | |
| 1436. |
A uniform wave have components |
| A. | in the perpendicular direction E existing while H is zero |
| B. | in the direction of propagation E existing while H is zero |
| C. | E and H are zero in direction perpendicular to direction of propagation |
| D. | E and H existing only in direction perpendicular to direction of propagation |
| Answer» E. | |
| 1437. |
The relative permeability is taken as unity for which of the following? |
| A. | Air |
| B. | Cobalt |
| C. | Vacuum |
| D. | Bismuth |
| Answer» B. Cobalt | |
| 1438. |
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. | |
| 1439. |
Equipotential surfaces about a point charge are in which one of the following forms? |
| A. | Sphere |
| B. | Planes |
| C. | Cylinders |
| D. | Cubes |
| Answer» B. Planes | |
| 1440. |
The value of susceptibility in case of vacuum is taken as |
| A. | zero |
| B. | 0.5 |
| C. | unity |
| D. | infinity |
| Answer» B. 0.5 | |
| 1441. |
__________ will have the least value of relative permeability. |
| A. | Palladium |
| B. | Silver |
| C. | Cobalt |
| D. | Iron |
| Answer» C. Cobalt | |
| 1442. |
For an ideal antenna, numerical value of directivity must be |
| A. | |
| B. | 0 |
| C. | 1 |
| D. | any value |
| Answer» B. 0 | |
| 1443. |
An electromagnetic wave is incident normally on a dielectric boundary. It is |
| A. | totally reflected |
| B. | partially reflected and partially refracted |
| C. | totally absorbed |
| D. | none of the above |
| Answer» C. totally absorbed | |
| 1444. |
According to maximum power transfer theorem, if the load is inductive, the source should be |
| A. | inductive |
| B. | capacitive |
| C. | resistive |
| D. | any of the above |
| Answer» C. resistive | |
| 1445. |
According to Siegel and Labus, antenna can be treated as |
| A. | closed transmission line |
| B. | shorted transmission line |
| C. | earthed transmission line |
| D. | opened-out transmission line |
| Answer» E. | |
| 1446. |
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 | |
| 1447. |
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 | |
| 1448. |
Cassegrain feed is used with a parabolic reflection to |
| A. | reduce the size of the main reflector |
| B. | increase the gain of the system |
| C. | increase the beamwidth of the system |
| D. | allow the feed to be placed at a convenient point |
| Answer» E. | |
| 1449. |
Select the correct relation |
| A. | (AB) = A B + B A |
| B. | . (AB) = A . B + A B |
| C. | x (AB) = A x B + A B |
| D. | All of the above |
| Answer» E. | |
| 1450. |
Diffraction of electromagnetic wave |
| A. | is caused by reflection from the ground |
| B. | may occur around the edge of a sharp obstacle |
| C. | arises only with spherical wavefronts |
| D. | none of these |
| Answer» C. arises only with spherical wavefronts | |