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.
| 751. |
When an electromagnetic wave travelling in one medium strikes upon a second medium (having a different conductivity) the wave will be |
| A. | totally transmitted |
| B. | totally reflected |
| C. | neither transmitted nor reflected |
| D. | partially transmitted and partially reflected |
| Answer» E. | |
| 752. |
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 | |
| 753. |
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. | |
| 754. |
In free space |
| A. | phase velocity is greater than light velocity |
| B. | phase velocity is equal to group velocity |
| C. | phase velocity is equal to light velocity |
| D. | Both (b) and (c) |
| Answer» E. | |
| 755. |
To couple a coaxial line to a parallel wire line, it is best to use a |
| A. | balun |
| B. | slotted line |
| C. | quarter wave transformer |
| D. | directional coupler |
| Answer» B. slotted line | |
| 756. |
A TV. transmitting aerial is fixed on top of a 150 metre tower located on a mountain 1200 m height. The range of transmitter is |
| A. | 51 km |
| B. | 152 km |
| C. | 152 m |
| D. | 51 m |
| Answer» C. 152 m | |
| 757. |
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 | |
| 758. |
Solution of Laplace equations, which are continuous through the second derivative, are called |
| A. | bessel functions |
| B. | odd functions |
| C. | harmonic functions |
| D. | fundamental functions |
| Answer» D. fundamental functions | |
| 759. |
If wave of critical frequency 30 MHz is departing at an angle of 60°, then the MUF is given to be |
| A. | 10 MHz |
| B. | 15 MHz |
| C. | 30 MHz |
| D. | 60 MHz |
| Answer» E. | |
| 760. |
A conductor is said to be perfect if it has __________ conductivity |
| A. | finite |
| B. | infinite |
| C. | unity |
| D. | zero |
| Answer» C. unity | |
| 761. |
The work done in moving a charge Q on an equipotential line for a distance d will be |
| A. | V/d |
| B. | QV/d |
| C. | Q.d |
| D. | zero |
| Answer» E. | |
| 762. |
Antenna radiation efficiency can be increased by |
| A. | reducing radiation resistance of the system |
| B. | increasing radiation resistance of the system |
| C. | providing effective earthing |
| D. | any of the above |
| Answer» C. providing effective earthing | |
| 763. |
The radiation pattern of a parabola antenna is |
| A. | omnidirectional |
| B. | a figure of directional |
| C. | highly directional |
| D. | none of the above |
| Answer» D. none of the above | |
| 764. |
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 | |
| 765. |
The maximum effective aperture of λ/2 (half-wave) antenna is |
| A. | 0.013 λ2 |
| B. | 0.13 λ2 |
| C. | 1.3 λ2 |
| D. | 13 λ2 |
| Answer» C. 1.3 Œª2 | |
| 766. |
The useful magnetic flux obtainable from any closed surface is |
| A. | unity |
| B. | constant |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» E. | |
| 767. |
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 | |
| 768. |
Which of following antenna does not depend upon the frequency? |
| A. | Log-periodic |
| B. | Parabolic |
| C. | Conical |
| D. | All of the above |
| Answer» B. Parabolic | |
| 769. |
The statement that the line integral of magnetic field about any closed path is exactly equal to the direct current enclosed by that path, is known as |
| A. | Ampere's circuital law |
| B. | Coulomb's law |
| C. | Electrostatic's theory |
| D. | None of the above |
| Answer» B. Coulomb's law | |
| 770. |
Power gain of an antenna in a given direction is the ratio of |
| A. | average power to maximum power |
| B. | radiation intensity in that direction to the total input radiated power |
| C. | radiation intensity in that direction to the average radiated power |
| D. | none of the above |
| Answer» C. radiation intensity in that direction to the average radiated power | |
| 771. |
At a particular time it is observed that the frequencies of F layer at Delhi is 3 MHz the maximum electron density is |
| A. | 11 x 1010 |
| B. | 1.1 x 1010 |
| C. | 0.11 x 1010 |
| D. | 11 x 1012 |
| Answer» B. 1.1 x 1010 | |
| 772. |
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. | |
| 773. |
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 | |
| 774. |
Antenna beamwidth is |
| A. | measure of directivity |
| B. | measure of angle |
| C. | measure of radiation pattern |
| D. | measure of power pattern |
| Answer» B. measure of angle | |
| 775. |
Which of the following is best excited from a waveguide? |
| A. | Discone |
| B. | Helical |
| C. | Biconical |
| D. | Horn |
| Answer» E. | |
| 776. |
If ωε is the displacement current factor and s is conduction current density factor then which of the following statements is incorrect? |
| A. | For a lossless dielectric σ = 0 |
| B. | For an imperfect dielectric σ = 0 |
| C. | For a dielectric ωε >> σ |
| D. | For a semiconductor ωε = σ |
| Answer» C. For a dielectric œâŒµ >> œÉ | |
| 777. |
In H-plane metal plate lens the travelling wave front is |
| A. | totally retarded |
| B. | retarded |
| C. | accelerated |
| D. | neither accelerated nor retarded |
| Answer» C. accelerated | |
| 778. |
In a uniform plane wave E and H are related by |
| A. | E/H = 1 |
| B. | E/H = ε/μ |
| C. | E/H = μ/ε |
| D. | none of the above |
| Answer» D. none of the above | |
| 779. |
Which layer is least important in high frequency propagation? |
| A. | D layer |
| B. | E layer |
| C. | F1 layer |
| D. | F2 layer |
| Answer» B. E layer | |
| 780. |
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 | |
| 781. |
In a rectangular waveguide if operating frequency is greater than cut off frequency then propagation constant is |
| A. | purely real |
| B. | purely imaginary |
| C. | equal to unit |
| D. | a complex number |
| Answer» C. equal to unit | |
| 782. |
For aeroplane and navigation frequency band is |
| A. | VLF |
| B. | UHF |
| C. | VHF |
| D. | EHF |
| Answer» C. VHF | |
| 783. |
If the electric field intensity is given by , the potential difference between x(2, 0, 0) and y(1, 2, 3) is |
| A. | +1 volt |
| B. | -1 volt |
| C. | +5 volt |
| D. | +6 volt |
| Answer» D. +6 volt | |
| 784. |
The refractive index of E layer, if angle of incidence is 30° |
| A. | 0.5 |
| B. | 0.25 |
| C. | 0 |
| D. | 1 |
| Answer» B. 0.25 | |
| 785. |
Laplacian of a scalar function V is |
| A. | gradient of V |
| B. | gradient of the gradient of V |
| C. | divergence of V |
| D. | divergence of the gradient of V |
| Answer» E. | |
| 786. |
In a carbon-zinc cell the function of the depolarizer is that |
| A. | it synthesizes the decomposed electrolyte |
| B. | it converts the produced hydrogen into water |
| C. | it absorbs the oxygen produced in the cell |
| D. | it prevents the fast chemical action on the zinc container |
| Answer» C. it absorbs the oxygen produced in the cell | |
| 787. |
The M.K.S. unit of magnetic field intensity is |
| A. | ampere |
| B. | ampere/metre |
| C. | volt |
| D. | volt/metre |
| Answer» C. volt | |
| 788. |
An antenna array pattern is to used for increasing |
| A. | gain |
| B. | directivity |
| C. | directive gain |
| D. | all |
| Answer» E. | |
| 789. |
An arrangement of several individual antennas to spaced and phased that their individual contributions combine in one preferred direction and cancel in all other directions, to get greater directive gain or directivity, is known as |
| A. | directional radiation of antennas |
| B. | antenna gain stability |
| C. | array of antennas |
| D. | none of the above |
| Answer» D. none of the above | |
| 790. |
A rhombic antenna is a |
| A. | resonant antenna |
| B. | non-resonant antenna |
| C. | coupled antenna |
| D. | none of the above |
| Answer» C. coupled antenna | |
| 791. |
The divergence of a vector is a scalar, while the curl of a vector is another |
| A. | scalar |
| B. | vector |
| C. | unit vector |
| D. | none of the above |
| Answer» C. unit vector | |
| 792. |
In microwave communication links, when fading due to rain attenuation occurs then technique adopted for solving the problem would include |
| A. | antenna replacement and feed correction |
| B. | amplitude timing and phase correction |
| C. | polarization shifting and code diversity |
| D. | path diversity and frequency diversity |
| Answer» E. | |
| 793. |
In electromagnetic wave polarization is caused by |
| A. | refraction |
| B. | reflection |
| C. | longitudinal nature of electromagnetic waves |
| D. | transverse nature of electromagnetic waves |
| Answer» E. | |
| 794. |
An antenna having an effective temperature of 27°K is fed into a microwave amplifier that has an effective noise temperature of 30 K. Calculate the available noise power per unit bandwidth |
| A. | 30 K |
| B. | 57 K |
| C. | 27 K |
| D. | 3K, K is Boltzmann constant |
| Answer» C. 27 K | |
| 795. |
The numerical value of directive gain may lie between |
| A. | 1 and + 1 |
| B. | 0 and 1 |
| C. | 0 and ‚àû |
| D. | 1 and ‚àû |
| Answer» D. 1 and ‚àû | |
| 796. |
For a hollow waveguide, the axial current must necessarily be |
| A. | combination of conduction and displacement current |
| B. | conduction current only |
| C. | time varying conduction current and displacement current |
| D. | displacement current only |
| Answer» E. | |
| 797. |
UHF and microwaves in the frequency range 300 MHz to 30 GHz can be best transmitted using __________ propagation |
| A. | sky wave |
| B. | ground wave |
| C. | duct |
| D. | none of the above |
| Answer» D. none of the above | |
| 798. |
Gain of isotropic antenna is |
| A. | 10 dB |
| B. | 0 dB |
| C. | ‚àû |
| D. | 1 dB |
| Answer» B. 0 dB | |
| 799. |
F2 layer of atmosphere extends from |
| A. | 250 km to 400 km |
| B. | 150 km to 250 km |
| C. | 50 km to 150 km |
| D. | 15 km to 50 km |
| Answer» B. 150 km to 250 km | |
| 800. |
The line of sight communication requires that transmit and receive antennas to face each other. If the transmit antenna is vertically polarized, for the best reception the receive antenna should be |
| A. | horizontally polarized |
| B. | vertically polarized |
| C. | at 45° with respect to horizontal polarization |
| D. | at 45° with respect to vertical polarization |
| Answer» B. vertically polarized | |