MCQOPTIONS
Saved Bookmarks
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.
| 1451. |
What does the expression represent? |
| A. | Electric Energy density |
| B. | Magnetic Energy density |
| C. | Power density |
| D. | Radiation Resistance |
| Answer» C. Power density | |
| 1452. |
For radiation field of an antenna at a distance r varies as |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/201-340-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/201-340-3.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/201-340-4.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/204-436-1.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/201-340-3.png"> | |
| 1453. |
Power gain of antenna equals directive gain in VHF and UHF range if and only if efficiency of the antenna is |
| A. | 0.25 |
| B. | 0.5 |
| C. | 0.75 |
| D. | 1 |
| Answer» E. | |
| 1454. |
A conductor is said to be perfect if it has __________ conductivity |
| A. | finite |
| B. | infinite |
| C. | unity |
| D. | zero |
| Answer» C. unity | |
| 1455. |
An electron when placed midway between two equal and opposite charges will |
| A. | remain stationary |
| B. | oscillate between the charges |
| C. | be thrown out of the field |
| D. | spin in the field |
| Answer» B. oscillate between the charges | |
| 1456. |
Which of the following is the abnormal phenomena observed in the ionosphere? |
| A. | Communication link interference |
| B. | Sun spot cycle |
| C. | Fading and whistlers |
| D. | Tides and winds |
| Answer» B. Sun spot cycle | |
| 1457. |
Which of the wave remains unaffected whether it is a day or night? |
| A. | Sky wave |
| B. | Ground wave |
| C. | Tropospheric wave |
| D. | Space wave |
| Answer» C. Tropospheric wave | |
| 1458. |
Which of the following is not an omnidirectional antenna? |
| A. | Log periodic |
| B. | Half-wave dipole |
| C. | Discone |
| D. | Marconi |
| Answer» B. Half-wave dipole | |
| 1459. |
In a loss-less transmission line |
| A. | R << L; G << C |
| B. | R = L, G = C |
| C. | R >> L; G >> C |
| D. | none of the above |
| Answer» B. R = L, G = C | |
| 1460. |
The unit of magnetic flux density is |
| A. | farad/metre |
| B. | ohm/metre |
| C. | tesla |
| D. | ampere/metre |
| Answer» D. ampere/metre | |
| 1461. |
Distances near the skip distance should be used for sky-wave propagation |
| A. | to avoid the Faraday effect |
| B. | to avoid tilting |
| C. | to prevent sky-wave and upper ray interference |
| D. | so as to exceed the critical frequency |
| Answer» D. so as to exceed the critical frequency | |
| 1462. |
End fire array has a dipole spacing of /2. |
| A. | True |
| B. | False |
| Answer» C. | |
| 1463. |
Which one of following is correct for broadside array? |
| A. | Direction of radiation is perpendicular to axis |
| B. | Also perpendicular to the plane |
| C. | Current is fed of equal amplitude equal phase |
| D. | All |
| Answer» E. | |
| 1464. |
The effective length of an antenna (Le) is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-321-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-321-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-321-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-321-4.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-321-3.png"> | |
| 1465. |
Curl of gradient A is |
| A. | x ( A) = 1 |
| B. | x ( A) = |
| C. | x ( A) = 0 |
| D. | x ( A) = - |
| Answer» D. x ( A) = - | |
| 1466. |
The simplest standing wave is due to the value of reflection co-efficient is |
| A. | -1 |
| B. | zero |
| C. | unity |
| D. | infinity |
| Answer» D. infinity | |
| 1467. |
In terrestrial microwave links, the number of 'fades' per unit increases as |
| A. | both the transmission and the distance between the antennas are increased |
| B. | the transmission frequency is increased but the distance between the antennas is decreased |
| C. | the transmission frequency is decreased but the distance between the antennas is increased |
| D. | both the transmission frequency and distance between the antennas are decreased |
| Answer» C. the transmission frequency is decreased but the distance between the antennas is increased | |
| 1468. |
Surface impedance at high frequencies is a consideration for |
| A. | good conductors |
| B. | semiconductors |
| C. | dielectrics |
| D. | ferrites |
| Answer» B. semiconductors | |
| 1469. |
Dish antennas are |
| A. | loop |
| B. | helical |
| C. | parabolic |
| D. | conical |
| Answer» D. conical | |
| 1470. |
The direction in a Yagi Uda antenna |
| A. | is longer than the radiating element |
| B. | is shorter than the radiating element |
| C. | can be longer or shorter than the radiating element |
| D. | does not exist |
| Answer» C. can be longer or shorter than the radiating element | |
| 1471. |
When a plane wave travelling in free space is incident normally on a medium having r = 4.0, then fraction of power transmitted into the medium is given by |
| A. | 8/9 |
| B. | 1/2 |
| C. | 1/3 |
| D. | 5/6 |
| Answer» B. 1/2 | |
| 1472. |
In cell phone antennas are |
| A. | monopole |
| B. | loops |
| C. | helical |
| D. | lens |
| Answer» B. loops | |
| 1473. |
Antenna commonly used for microwave links are |
| A. | loop antennas |
| B. | log periodic antennas |
| C. | paraboloidal dishes |
| D. | rhombic antennas |
| Answer» D. rhombic antennas | |
| 1474. |
Magnesium is alloyed with conducting materials for antenna primarily with the purpose of |
| A. | increasing efficiency |
| B. | improving radiative power |
| C. | reducing weight |
| D. | increasing density |
| Answer» D. increasing density | |
| 1475. |
Electric lines of force do not cross each other because |
| A. | the lines of force mutually repel each other |
| B. | the lines of force emanate from a point charge |
| C. | the tangent to the line of force gives the direction of E and if they cross two tangents for E which is not possible |
| D. | none of the above |
| Answer» D. none of the above | |
| 1476. |
A person with a receiver is 5 km away from the transmitter. What is the distance that this person must move further to detect at 3 dB decrease in signal strength? |
| A. | 942 m |
| B. | 2070 m |
| C. | 4978 m |
| D. | 5320 m |
| Answer» C. 4978 m | |
| 1477. |
SHF range is |
| A. | 30 - 300 MHz |
| B. | 300 - 3000 MHz |
| C. | 3000 - 30000 MHz |
| D. | 30000 - 300000 MHz |
| Answer» D. 30000 - 300000 MHz | |
| 1478. |
The disturbance from adjacent power lines is known as |
| A. | cross talk |
| B. | cross fire |
| C. | inductive disturbance |
| D. | none of the above |
| Answer» D. none of the above | |
| 1479. |
Which of the following term applies to troposcatter propagation? |
| A. | SIDs |
| B. | Faraday rotation |
| C. | Atmospheric storms |
| D. | Fading |
| Answer» E. | |
| 1480. |
Two co-axial cylindrical sheets of charge are present in free space fs = 5 c/m2 at r = 2 m and rs = -2 c/m2 at r = 4 m, The displacement flux density at r = 3 m is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/199-287-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/199-287-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/199-287-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/199-287-4.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/199-287-4.png"> | |
| 1481. |
The bidirectional pattern of a broadside array can be converted into unidirectional by |
| A. | maintaining the distance of /4 between the elements |
| B. | maintaining the distance of /2 between the elements |
| C. | installing an identical array behind the main array at distance /4 and exciting it by current leading in phase by 90 |
| D. | installing an identical array behind the main array at distance /2 and exciting it by current leading in phase by 120 |
| Answer» D. installing an identical array behind the main array at distance /2 and exciting it by current leading in phase by 120 | |
| 1482. |
The radiation pattern of two element collinear array is represent in |
| A. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-467-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-467-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-467-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-467-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-467-2.png"> | |
| 1483. |
The L/C has the dimension of |
| A. | time |
| B. | capacitance |
| C. | velocity |
| D. | resistance |
| Answer» E. | |
| 1484. |
VLF waves are used for communication system because |
| A. | of low power requirement |
| B. | they are least prone to distortion |
| C. | they penetrate the ionosphere easily |
| D. | the transmitting antennas are of convenient size |
| Answer» D. the transmitting antennas are of convenient size | |
| 1485. |
The value of VSWR is taken as when the line is |
| A. | short-circuited |
| B. | open-circuited |
| C. | terminated with full load |
| D. | terminated with load equal to the characteristic impedance of the load |
| Answer» C. terminated with full load | |
| 1486. |
The wavelength of an electromagnetic wave after reflection at angle on a surface |
| A. | remains same as the wavelength perpendicular to the surface |
| B. | remains same in the free space |
| C. | increases in actual direction of propagation |
| D. | decreases in actual direction of propagation |
| Answer» C. increases in actual direction of propagation | |
| 1487. |
A higher value of Standing Wave Ratio indicates |
| A. | least mismatch between line and load |
| B. | greater mismatch between load and line |
| C. | number of nodes is equal to the number of antinodes |
| D. | none of the above |
| Answer» C. number of nodes is equal to the number of antinodes | |
| 1488. |
An end fire array consisting of several half-wave lengths of directive gain 40, then Find width of major lobe for broadside |
| A. | 6 |
| B. | 5.73 |
| C. | 51.25 |
| D. | 0 |
| Answer» C. 51.25 | |
| 1489. |
2V = - r/E is known as __________ equation |
| A. | Poisson |
| B. | Fourier |
| C. | Laplace |
| D. | Maxwell |
| Answer» B. Fourier | |
| 1490. |
A vertical earthed antenna is resonant when its physical height is equal to |
| A. | |
| B. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/201-355-1.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/206-479-1.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/198-273-1.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/198-273-1.png"> | |
| 1491. |
A wavelength of 1 mm could be expected in |
| A. | VLF |
| B. | HF |
| C. | EHF |
| D. | SHF |
| Answer» D. SHF | |
| 1492. |
The numerical value of directivity of current element of half-wave dipole is 1.76 and 2.15 dB respectively. The directive gain of half-wave dipole over current element will be |
| A. | 3.91 dB |
| B. | 1.95 dB |
| C. | 0.39 dB |
| D. | 0.195 dB |
| Answer» D. 0.195 dB | |
| 1493. |
The maximum effective aperture of an antenna which is operating at wavelength of 2 m and has directivity of 100 is |
| A. | 15.92 |
| B. | 31.84 |
| C. | 2.18 |
| D. | 3.184 |
| Answer» E. | |
| 1494. |
The current distribution of a half wave dipole is |
| A. | uniform |
| B. | sinusoidal |
| C. | triangular |
| D. | complex |
| Answer» C. triangular | |
| 1495. |
The waveguides compared to equivalent transmission lines at low frequency are |
| A. | able to carry more power |
| B. | less noisy |
| C. | having lower attenuation |
| D. | all of the above |
| Answer» E. | |
| 1496. |
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 | |
| 1497. |
To couple a coaxial line to a parallel to wire line it is best to use a |
| A. | slotted line |
| B. | balun |
| C. | directional coupler |
| D. | quarter wave transformer |
| Answer» C. directional coupler | |
| 1498. |
The intrinsic impedance of free space |
| A. | increases with increase of frequency |
| B. | decreases with increase of frequency |
| C. | is independent of frequency |
| D. | none |
| Answer» D. none | |
| 1499. |
A dipole antenna was radiating with some excitation in free space radiating a certain amount of the power. If this antenna is immersed in a lake where water is non-dissipative but has a dielectric constant of 81, the radiated power with the same excitation will |
| A. | decrease to finite non-zero value |
| B. | remain the same |
| C. | increase |
| D. | decrease to zero |
| Answer» C. increase | |
| 1500. |
The input impedance of short-circuited line of length l where l < /4 |
| A. | inductive |
| B. | capacitive |
| C. | resistive |
| D. | none of the above |
| Answer» B. capacitive | |