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.
| 551. |
The effective length of an antenna (Le) is |
| A. | |
| B. | |
| Answer» C. | |
| 552. |
Maximum effective aperture (Ae)max of short dipole antenna is |
| A. | 1.119 λ2 |
| B. | 0.119 λ2 |
| C. | 1.19 λ2 |
| D. | 1.919 λ2 |
| Answer» C. 1.19 Œª2 | |
| 553. |
Which of following antenna not produces circular polarisation? |
| A. | Helical |
| B. | Parabolic |
| C. | Disc |
| D. | Yagi |
| Answer» E. | |
| 554. |
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 | |
| 555. |
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 | |
| 556. |
Unit of e is __________ . |
| A. | Farad/metre |
| B. | Farad2/metre |
| C. | 1 |
| D. | |
| Answer» D. | |
| 557. |
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 | |
| 558. |
The reflection coefficient is generally a |
| A. | complex number |
| B. | fraction |
| C. | imaginary number |
| D. | none of the above |
| Answer» B. fraction | |
| 559. |
Considerable ionization occurs between the range |
| A. | 50 km to 400 km |
| B. | 100 to 400 km |
| C. | 50 km to 250 km |
| D. | 10 to 50 km |
| Answer» B. 100 to 400 km | |
| 560. |
A waveguide operated below cut off frequency can be used as |
| A. | an isolator |
| B. | none |
| C. | The conduction current is equal to the displacement current |
| D. | The conduction current density is J and displacement current density |
| Answer» C. The conduction current is equal to the displacement current | |
| 561. |
For an antenna radiation and induction fields are |
| A. | |
| B. | |
| Answer» C. | |
| 562. |
A 50 p characteristic impedance line is connected to a load which shows a reflection coefficients of 0.268. If Vin = 15 volt, then the net power delivered to the load will be |
| A. | 0.139 W |
| B. | 1.39 W |
| C. | 0.278 W |
| D. | 2.78 W |
| Answer» C. 0.278 W | |
| 563. |
In a lead acid cell the density of the acid gives an indication of |
| A. | the charge of the battery |
| B. | the e.m.f. of the battery |
| C. | Connecting an inductance at the end |
| D. | Connecting a short circuited stub at the load |
| Answer» D. Connecting a short circuited stub at the load | |
| 564. |
In a waveguide if TE mode exist for z direction propagation, then |
| A. | Ez = 0, Hz ≠ 0 |
| B. | Ez = 0, Hz = 0 |
| C. | Ez ≠ 0, Hz = 0 |
| D. | Ez ≠ 0, Hz ≠ 0 |
| Answer» B. Ez = 0, Hz = 0 | |
| 565. |
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. | |
| 566. |
The disturbance from adjacent telephone line is known as |
| A. | cross fire |
| B. | cross talk |
| C. | inductive disturbance |
| D. | none of the above |
| Answer» C. inductive disturbance | |
| 567. |
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) | |
| 568. |
The unit of displacement density is |
| A. | volt/metre |
| B. | ampere/metre2 |
| C. | coulombs/metre |
| D. | coulombs/metre2 |
| Answer» E. | |
| 569. |
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 | |
| 570. |
Consider the following; for a loss-less transmission line we can write, Zin = - jz0 for a shorted line with l = λ/8Zin = ± j ∞ for a shorted line with l = λ/4Zin= jz0 for an open line with l = λ/2Zin = 0 for a matched line of any length Select the correct answer using the codes given below codes. |
| A. | 1, 2 |
| B. | 2, 3 |
| C. | 1, 3 |
| D. | 2, 4 |
| Answer» E. | |
| 571. |
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. | |
| 572. |
Which of the following constitute the loss resistance of an antenna? |
| A. | Loss in earth connections |
| B. | All of the above |
| C. | ampere |
| D. | ampere/metre |
| Answer» E. | |
| 573. |
The power gain of a half-wave dipole with respect to an isotropic radiator is |
| A. | 2.15 db |
| B. | 3 db |
| C. | 4.15 db |
| D. | 6 db |
| Answer» B. 3 db | |
| 574. |
The effective electrical length of an antenna is __________ its physical length |
| A. | greater than |
| B. | equal to |
| C. | less than |
| D. | none of the above |
| Answer» B. equal to | |
| 575. |
Which antenna is frequently used for local area transmission at UHF/VHF? |
| A. | Slot antenna |
| B. | Loop antenna |
| C. | V/d |
| D. | QV/d |
| Answer» B. Loop antenna | |
| 576. |
The pure capacitor connected across an A.C. voltage consumed 20 W. This is due to |
| A. | the capacitive reactance in ohms |
| B. | the current flowing in the capacitor |
| C. | the fused capacitor was a big one |
| D. | none of the above |
| Answer» E. | |
| 577. |
An electromagnetic wave incident on a perfect conductor is |
| A. | fully transmitted |
| B. | partially transmitted |
| C. | entirely reflected |
| D. | none of the above |
| Answer» D. none of the above | |
| 578. |
VSWR is related with reflection co-efficient as |
| A. | VSWR = 1 + |k| |
| B. | VSWR = 1 - |k| |
| C. | the value of current |
| D. | the weight of the conductor |
| Answer» C. the value of current | |
| 579. |
A rectangular waveguide measures 3 x 4.5 cm internally and has a 10 GHz signal propagated in it. Calculate the cut off frequency for dominant mode. |
| A. | 4 GHz |
| B. | 7.5 GHz |
| C. | 5 GHz |
| D. | 10 GHz |
| Answer» D. 10 GHz | |
| 580. |
In case of antenna the ratio of the power radiated in the desired direction to the power radiated in the opposite direction is known as |
| A. | transmission efficiency |
| B. | front to back ratio |
| C. | loss coefficient |
| D. | none of the above |
| Answer» C. loss coefficient | |
| 581. |
For a wave propagating in air filled rectangular waveguide. |
| A. | guide wavelength is never less than free space wavelength. |
| B. | wave impedance is never less than the free space impedance |
| C. | TEM mode is possible if the dimension of the waveguide are properly chosen. |
| D. | propagation constant is a real quantity. |
| Answer» B. wave impedance is never less than the free space impedance | |
| 582. |
The ionosphere plays a significant role in radio wave propagation at |
| A. | high frequency |
| B. | ultra-high frequencies |
| C. | microwave frequency |
| D. | optical frequencies |
| Answer» B. ultra-high frequencies | |
| 583. |
For resonant long wire antenna 'n' half wavelength long in free space, if 'n' is increased then inclination of the major lobe with wire axis will __________ . |
| A. | remains same |
| B. | none |
| C. | 0.013 λ2 |
| D. | 0.13 λ2 |
| Answer» C. 0.013 Œª2 | |
| 584. |
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 | |
| 585. |
Mutual impedance is not depend upon |
| A. | magnitude of induced current |
| B. | tuning condition |
| C. | self impedance |
| D. | phase relationship between induced and original currents |
| Answer» D. phase relationship between induced and original currents | |
| 586. |
An antenna having a high Q has |
| A. | lower BW |
| B. | higher BW |
| C. | flat response |
| D. | none of the above |
| Answer» B. higher BW | |
| 587. |
The effective height of an antenna is slightly greater than physical height because |
| A. | wave velocity in conductor is less than its velocity in free space |
| B. | wave velocity in conductor is more than its velocity in free space |
| C. | resistance of conductor is less than that of free space |
| D. | none of the above |
| Answer» B. wave velocity in conductor is more than its velocity in free space | |
| 588. |
A microwave link uses only line-of-sight propagation. |
| A. | 1 |
| B. | |
| C. | equal to its group velocity |
| D. | less than the velocity of light in free space |
| Answer» B. | |
| 589. |
Which of the following is not a wideband antenna? |
| A. | Marconi |
| B. | Discone |
| C. | Helical |
| D. | Folded dipole |
| Answer» B. Discone | |
| 590. |
The distance between maxima and minima of a standing wave is |
| A. | λ/4 |
| B. | λ/2 |
| C. | λ |
| D. | 2λ |
| Answer» B. Œª/2 | |
| 591. |
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 | |
| 592. |
Poynting theorem relates the electric intensity E, magnetic intensity H to the rate of energy flow per unit area at a point P as |
| A. | P = E/H |
| B. | P = H/E |
| C. | E = 1/E x H |
| D. | P = E x H |
| Answer» E. | |
| 593. |
The voltage and current distributions on a grounded λ/4 dipole (Marconi antenna) are similar to those of a half wave dipole in space. |
| A. | 1 |
| B. | |
| C. | Poisson's equation |
| D. | Kirchoff's node equation |
| Answer» B. | |
| 594. |
If a and b are the dimensions of waveguide then |
| A. | a = 3b |
| B. | a = 2b |
| C. | a = b |
| D. | a = b/4 |
| Answer» C. a = b | |
| 595. |
In case of antenna the lower value of Q indicates |
| A. | higher bandwidth |
| B. | lower bandwidth |
| C. | higher distortion |
| D. | lower distortion |
| Answer» B. lower bandwidth | |
| 596. |
The input impedance for folded dipole antenna (two half dipole) is |
| A. | 73 n2 |
| B. | 377 n2 |
| C. | 73 n |
| D. | 377 n |
| Answer» B. 377 n2 | |
| 597. |
A medium of relative permittivity εr2 = 2 forms an interface with free space. A point source of EM energy is located in the medium at a depth of 1 meter from the interface. Due to the total internal reflection, the transmitted beam has a circular cross-section over the interface. The area of the beam cross section at the interface is given by |
| A. | 2p m2 |
| B. | p2 m2 |
| C. | m2 |
| D. | p m2 |
| Answer» E. | |
| 598. |
The main difference between the broadside arrays and end fire arrays is that |
| A. | individual elements are fed with same current in broadside arrays and of different magnitude in end fire arrays |
| B. | in broadside arrays the elements are equidistant whereas in end fire array the distance between elements increases progressively |
| C. | the total number of elements in broadside array is always one and a half times that of elements in end fire arrays |
| D. | in broadside array the individual elements are fed in, out of phase by 180° whereas in end fire array individual elements are fed with currents of equal magnitude but their phases vary progressively along the line in such a way as to make the entire arrangement substantially unidirectional |
| Answer» E. | |
| 599. |
The total electrical energy emitted overall space from an electron of charge e and radius r is |
| A. | e/ε0r2 |
| B. | e2/ε0r |
| C. | e2/4pε0r2 |
| D. | e2/8pε0r |
| Answer» E. | |
| 600. |
Parabolic and lens antenna used at |
| A. | microwave frequency |
| B. | medium frequency |
| C. | low frequency |
| D. | high frequency |
| Answer» B. medium frequency | |