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.
| 701. |
Which one of the following statement is not a correct for a plane wave with = 0.5e-0.1x cos (106t - 2x)az A/m? |
| A. | The wave frequency is 10-6 r.p.s. |
| B. | The wavelength is 3.14 m |
| C. | The wave travels + x direction |
| D. | Wave is polarized in the z direction. |
| Answer» E. | |
| 702. |
Analysis of EM wave in waveguide based on |
| A. | circuit theory |
| B. | field theory |
| C. | optical theory |
| D. | both (a) and (b) |
| Answer» C. optical theory | |
| 703. |
The main disadvantage of the two-hole directional coupler is |
| A. | poor directivity |
| B. | narrow bandwidth |
| C. | high standing wave ratio |
| D. | low directional coupling |
| Answer» C. high standing wave ratio | |
| 704. |
Which of the following relations is incorrect? |
| A. | mmf x reluctance = 1 |
| B. | conductance x resistance = 1 |
| C. | |
| Answer» B. conductance x resistance = 1 | |
| 705. |
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 | |
| 706. |
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 | |
| 707. |
Loop antennas are mostly employed for direction finding (DF) purposes because they are small and hence portable. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 708. |
Which of the following is the main difference between waveguide and transmission line? |
| A. | Waveguides cannot be coupled to coaxial lines |
| B. | Waveguides have no standing wave ratio |
| C. | Transmission line does not suffer from the effect of low cut off frequency |
| D. | Waveguides are not distributed like transmission lines |
| Answer» D. Waveguides are not distributed like transmission lines | |
| 709. |
For free space propagation |
| A. | γ = a + jβ |
| B. | γ = jβ |
| C. | γ = a |
| D. | a = β = 0 |
| Answer» B. Œ≥ = jŒ≤ | |
| 710. |
In cell phone antennas are |
| A. | monopole |
| B. | loops |
| C. | helical |
| D. | lens |
| Answer» B. loops | |
| 711. |
The propagation constant of a transmission line is |
| A. | |
| B. | (R + jωL)(G + ωC) |
| Answer» C. | |
| 712. |
Transverse electric (TE) waves have |
| A. | electric field component E in the direction of propagation |
| B. | magnetic field component H in the direction of propagation |
| C. | magnetic field component H in the direction of propagation and no component of electric field E in this direction |
| D. | electric field component E in the direction of propagation and no component of magnetic field H in this direction |
| Answer» D. electric field component E in the direction of propagation and no component of magnetic field H in this direction | |
| 713. |
Maximum power transfer will take place in a practical antenna if (XL = Load Reactance, XA Antenna Reactance) |
| A. | XL = - XA |
| B. | XL = XA |
| C. | XL = XA |
| D. | XL = XA2 |
| Answer» B. XL = XA | |
| 714. |
When a line of any odd multiple of a quarter wavelength is short-circuited it represents |
| A. | unit impedance |
| B. | infinite impedance |
| C. | zero impedance |
| D. | none of the above |
| Answer» C. zero impedance | |
| 715. |
Whereas resonant antenna is bidirectional, non-resonant antenna is unidirectional. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 716. |
A dominant wave is characterised by which of the following? |
| A. | No attenuation |
| B. | Lowest cut off wavelength |
| C. | Highest cut off wavelength |
| D. | All of the above |
| Answer» D. All of the above | |
| 717. |
When the height of a vertical earthed antenna is less than λ/4 |
| A. | the base input impedance will be capacitive |
| B. | the base input impedance will be purely resistive |
| C. | the base input impedance will be inductive |
| D. | the base input impedance will be negligibly small |
| Answer» B. the base input impedance will be purely resistive | |
| 718. |
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. | |
| 719. |
Maximum usable frequency is [fmuf] |
| A. | fc sec i |
| B. | fc cos i |
| C. | fc sin i |
| D. | fc sec i |
| Answer» B. fc cos i | |
| 720. |
The effect of the inductance of a coil on a constant direct current is that |
| A. | it does not effect the constant direct current |
| B. | it decreases the current |
| C. | it strengthens the current |
| D. | it causes a higher voltage drop |
| Answer» B. it decreases the current | |
| 721. |
Which of the following is multiband HF receiving antenna? |
| A. | Square loop |
| B. | Log-periodic |
| C. | Conical horn |
| D. | Folded dipole |
| Answer» C. Conical horn | |
| 722. |
In binomial arrays the elimination of secondary lobes takes place |
| A. | at the cost of directivity |
| B. | at the cost of gain |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» D. none of the above | |
| 723. |
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¬∞ | |
| 724. |
The current distribution along a travelling wave antenna can be written in the form |
| A. | f(z) = f0e-jβz |
| B. | f(z) = f0 sin βz |
| C. | f(z) = f0 |
| D. | f(z) = f0 cos (ωt - βz) |
| Answer» E. | |
| 725. |
Triatics are |
| A. | small height antenna directly mounted on jeeps, ships, etc. |
| B. | the towers or masts which are used as radiators |
| C. | the towers or masts which are not used as radiators |
| D. | supports for antenna conductors. |
| Answer» D. supports for antenna conductors. | |
| 726. |
Calculate the wave number in waveguide having dimensions 4 x 2 cm at 3 GHz |
| A. | 6.28 |
| B. | 62.8 |
| C. | 8 |
| D. | 0 |
| Answer» C. 8 | |
| 727. |
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 | |
| 728. |
While determining antenna height for terrestrial microwaves links, the effect of refraction from the atmosphere is taken care of by considering the effective curvature of the earth to be |
| A. | times the radius of the earth (Re) |
| B. | Re |
| C. | Re |
| D. | Re |
| Answer» D. Re | |
| 729. |
A rectangular waveguide is a |
| A. | rectangular conducting wire to propagate electromagnetic waves |
| B. | hollow rectangular walled room carrying electromagnetic wave |
| C. | hollow rectangular conducting tube through which electromagnetic waves can be propagated |
| D. | tube antenna to transmit and receive electromagnetic waves |
| Answer» D. tube antenna to transmit and receive electromagnetic waves | |
| 730. |
Strip lines are used at |
| A. | microwave frequency |
| B. | low frequency |
| C. | High frequency |
| D. | at any frequency |
| Answer» B. low frequency | |
| 731. |
The best excited reflector from a wave guide is |
| A. | horn |
| B. | parabolic |
| C. | biconical |
| D. | corner |
| Answer» B. parabolic | |
| 732. |
According to maximum power transfer theorem, the maximum power is absorbed by one network from another network when |
| A. | the impedance of one of the networks is half that of the other |
| B. | the impedance of one is the complex conjugate of the other |
| C. | the impedance of one is equal to that of the other |
| D. | none of the above |
| Answer» C. the impedance of one is equal to that of the other | |
| 733. |
Conductivity is measured in terms of |
| A. | mho/metre |
| B. | ohm/metre |
| C. | mho/metre2 |
| D. | ohm/metre2 |
| Answer» B. ohm/metre | |
| 734. |
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. | |
| 735. |
Radar antennas are usually |
| A. | dipoles |
| B. | yagi antennas |
| C. | parabolic dishes |
| D. | none of the above |
| Answer» D. none of the above | |
| 736. |
For TM waves in a parallel plate waveguide, the minimum attenuation arising from imperfect conductors would occur at a freq. of (fc is the cut off frequency) |
| A. | 3 fc |
| B. | 3 fc |
| C. | 2 fc |
| D. | 2 fc |
| Answer» E. | |
| 737. |
A satellite that simply reflect back the signals from one region of the earth to the other region is known as |
| A. | orbiting satellite |
| B. | geostationary satellite |
| C. | active satellite |
| D. | passive satellite |
| Answer» E. | |
| 738. |
Which of the following term applies to troposcatter propagation? |
| A. | SIDs |
| B. | Faraday rotation |
| C. | Atmospheric storms |
| D. | Fading |
| Answer» E. | |
| 739. |
The frequency range for satellite communication is |
| A. | 3 to 30 kHz |
| B. | 300 to 3000 kHz |
| C. | 3000 to 30000 MHz |
| D. | 30000 to 300000 MHz |
| Answer» D. 30000 to 300000 MHz | |
| 740. |
Isotropic radiator is one that radiates energy |
| A. | uniformly in all direction |
| B. | inside a hollow sphere |
| C. | in a well defined isotropic direction |
| D. | none of the above |
| Answer» B. inside a hollow sphere | |
| 741. |
In broadside array |
| A. | the principle direction radiation is perpendicular to the array axis and also to the plane containing the array elements |
| B. | the principle direction radiation is parallel to the array axis and also to the plane containing the array elements |
| C. | the principle direction radiation is parallel to the array axis and perpendicular to the plane containing the array elements |
| D. | the principle direction radiation is perpendicular to the array axis and parallel to the plane containing the array elements |
| Answer» B. the principle direction radiation is parallel to the array axis and also to the plane containing the array elements | |
| 742. |
In radar system if the antenna diameter is increased by a factor of 4, the minimum range will increased by a factor of |
| A. | 1 |
| B. | 2 |
| C. | 22 |
| D. | 4 |
| Answer» E. | |
| 743. |
Maxwell's curl equation for the static electric field E can be expressed as |
| A. | Δ x E = 0 |
| B. | Δ x E = constant |
| C. | Δ - E = constant |
| D. | Δ . E = 0 |
| Answer» B. Œî x E = constant | |
| 744. |
Which of the following frequencies cannot be used for reliable beyond-the-horizon terrestrial communications without repeaters? |
| A. | 25 kHz |
| B. | 15 MHz |
| C. | 750 MHz |
| D. | 12 GHz |
| Answer» E. | |
| 745. |
For broadside array, maxima will be obtain at |
| A. | 90°, 270° |
| B. | 180° |
| C. | 45° |
| D. | at any angle |
| Answer» B. 180¬∞ | |
| 746. |
If a wave is propagated in free space, it will be in nature of |
| A. | TE |
| B. | TM |
| C. | TEM |
| D. | Any one of above |
| Answer» D. Any one of above | |
| 747. |
The magnetic field intensity vector of a plane wave is given by (x, y, z, t) = 10 sin (5000t + 0.004x + 30 ), where denotes unit vector in y direction the wave is propagating with a phase velocity. |
| A. | 5 x 104 m/sec |
| B. | -3 x 108 m/sec |
| C. | -1.25 x 107 m/sec |
| D. | 3 x 108 m/sec |
| Answer» D. 3 x 108 m/sec | |
| 748. |
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 | |
| 749. |
Δ2V = - r/E is known as __________ equation |
| A. | Poisson |
| B. | Fourier |
| C. | Laplace |
| D. | Maxwell |
| Answer» B. Fourier | |
| 750. |
The length of half-wave antenna is at 30 MHz |
| A. | 2.5 meter |
| B. | 5 meter |
| C. | 10 meter |
| D. | 100 meter |
| Answer» C. 10 meter | |