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.
| 601. |
The electric intensity for free space is given by |
| A. | ε0d |
| B. | σ/ε0 |
| C. | σ.ε0 |
| D. | d/ε0 |
| Answer» D. d/Œµ0 | |
| 602. |
The bidirectional pattern of a broadside array can be converted into unidirectional by |
| A. | maintaining the distance of λ/4 between the elements |
| B. | maintaining the distance of λ/2 between the elements |
| C. | installing an identical array behind the main array at distance λ/4 and exciting it by current leading in phase by 90° |
| D. | installing an identical array behind the main array at distance λ/2 and exciting it by current leading in phase by 120° |
| Answer» D. installing an identical array behind the main array at distance Œª/2 and exciting it by current leading in phase by 120¬∞ | |
| 603. |
The term __________ applies to troposcatter propagation |
| A. | SIDS |
| B. | atmospheric storms |
| C. | coulomb/newton-metre |
| D. | coulomb2/newton-metre |
| Answer» C. coulomb/newton-metre | |
| 604. |
If the electric field intensity associated with a uniform plane electromagnetic wave travelling in a perfect dielectric medium is given by E(z, t) = 10 cos (2p x 107t - 0.1 pz) volt/metre, then the velocity of the travelling wave is |
| A. | 3.0 x 108 m/sec |
| B. | 2 x 108 m/sec |
| C. | 6.28 x 107 m/sec |
| D. | 2 x 107 m/sec |
| Answer» C. 6.28 x 107 m/sec | |
| 605. |
Which of the following will increase the antenna radiation efficiency? |
| A. | Top loading of antenna |
| B. | Any of the above |
| C. | phase shifter |
| D. | an attenuator |
| Answer» D. an attenuator | |
| 606. |
The essential condition for antenna array to be linear is that |
| A. | individual antennas of the array must be of equal size |
| B. | individual antennas of the array must be equally spaced along a straight line |
| C. | any two individual antennas of the array must not be in the same direction |
| D. | none of the above |
| Answer» C. any two individual antennas of the array must not be in the same direction | |
| 607. |
Surface waves can propagate on Piezoelectric substrates. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 608. |
A rectangular waveguide having TE10 mode as dominant mode is having a cut off frequency of 18 GHz for the TE30 mode. The inner broad wall dimension of the rectangular waveguide is |
| A. | 5/3 cm |
| B. | 5 cm |
| C. | 5/2 cm |
| D. | 10 cm |
| Answer» D. 10 cm | |
| 609. |
Which of the following does not characterize a ferromagnetic material? |
| A. | Coercivity |
| B. | Permeability |
| C. | Permittivity |
| D. | Reluctance |
| Answer» D. Reluctance | |
| 610. |
The force acting on a charge q moving with velocity in a region of electric field and magnetic field is |
| A. | r + x |
| B. | q( + x ) |
| C. | q( + x ) |
| D. | q |
| Answer» D. q | |
| 611. |
Many circles are drawn in a Smith chart used for transmission line calculations. The circle shown in the figure represents |
| A. | unit circles |
| B. | constant resistance circles |
| C. | constant reactance circles |
| D. | constant reflection coefficient circles |
| Answer» C. constant reactance circles | |
| 612. |
A perfect conductor is a perfect absorber of electromagnetic waves. |
| A. | 1 |
| B. | |
| C. | the level of the acid |
| D. | the eventual damages caused to the plates |
| Answer» B. | |
| 613. |
A medium is said to be isotropic when |
| A. | ‚àà = 0 |
| B. | ∈ = μ |
| C. | ∈ = σ |
| D. | ‚àà is scalar constant |
| Answer» E. | |
| 614. |
The unit of magnetic flux density is |
| A. | farad/metre |
| B. | ohm/metre |
| C. | tesla |
| D. | ampere/metre |
| Answer» D. ampere/metre | |
| 615. |
For transmission of waveform a dielectric medium of permittivity ε1 into a dielectric medium of lower permittivity ε2 , (ε1 > ε2) the critical angle of incidence θc (relative to the interface) is given by |
| A. | sin-1 |
| B. | cos-1 |
| C. | tan-1 |
| Answer» D. | |
| 616. |
Which of the following is high frequency transmission line? |
| A. | An impedance transformer |
| B. | Frequency compensator |
| C. | Flying resistor |
| D. | None of the above |
| Answer» B. Frequency compensator | |
| 617. |
If H = 0.1 sin (108p t + βλ) A/m for a plane wave propagating in free space, then the time average Poynting vector is |
| A. | (0.6psin2 βy) w/m2 |
| B. | - 0.6p w/m2 |
| C. | 1.2p w/m2 |
| D. | - 1.2p w/m2 |
| Answer» E. | |
| 618. |
For frequencies upto 1650 kHz __________ antenna is used |
| A. | yagi |
| B. | grounded |
| C. | turnstile |
| D. | marconi |
| Answer» B. grounded | |
| 619. |
The velocity factor of a transmission line |
| A. | mainly depends on the skin effect |
| B. | is always higher for a solid dielectric than for air |
| C. | mainly depends on the dielectric constant of the material used |
| D. | increases the velocity along the transmission line |
| Answer» D. increases the velocity along the transmission line | |
| 620. |
Divergence of curl A is |
| A. | ‚àá . (‚àá x A) = 1 |
| B. | ‚àá . (‚àá x A) = 0 |
| C. | ‚àá . (‚àá x A) = ‚àá |
| D. | ‚àá . (‚àá x A) = - ‚àû |
| Answer» C. ‚àá . (‚àá x A) = ‚àá | |
| 621. |
Broadcasting antennas are generally |
| A. | omnidirectional type |
| B. | vertical type |
| C. | horizontal type |
| D. | helical |
| Answer» C. horizontal type | |
| 622. |
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. | |
| 623. |
There is no radiation at right angles to the plane of the array, is end fire array. |
| A. | 1 |
| B. | |
| C. | Dielectric loss |
| D. | Leakage loss in insulation |
| Answer» B. | |
| 624. |
Directivity and beamwidth is related as |
| A. | D ‚àù B |
| B. | D ‚àù 1/B |
| C. | D ‚àù B |
| D. | D ‚àù B2 |
| Answer» C. D ‚àù B | |
| 625. |
The characteristic impedance of loss less transmission line is |
| A. | 1/LC |
| B. | C/L |
| C. | combination of conduction and displacement current |
| D. | conduction current only |
| Answer» C. combination of conduction and displacement current | |
| 626. |
A T.V. station works at 300 MHz and radiates 100 kW of power. This signal received at a distance of 200 km will be |
| A. | a few μV/m due to attenuation by atmosphere |
| B. | 1-5 mV due to ionospheric reflection |
| C. | nil since propagation is line of sight |
| D. | nil because signal fades completely at 300 MHz |
| Answer» D. nil because signal fades completely at 300 MHz | |
| 627. |
Transverse magnetic (TM) waves have |
| A. | magnetic field component H in the direction of propagation |
| B. | electric field component E 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» E. | |
| 628. |
For the same length of arrays, half power beam-width of binomial array |
| A. | is equal to that of uniform arrays |
| B. | is less than that of uniform array |
| C. | is more than that of uniform array |
| D. | is negligible as compared to that of uniform array |
| Answer» D. is negligible as compared to that of uniform array | |
| 629. |
A rectangular waveguide measures 3 x 4.5 cm internally and has a 10 GHz signal propagated in it. Calculate the guide wavelength for dominant mode. |
| A. | 13.5 m |
| B. | 3 m |
| C. | 88/3 m |
| D. | 3/88 m |
| Answer» E. | |
| 630. |
MUF is depend upon |
| A. | electron density of the ionospheric layer |
| B. | 11 year sun spot cycle |
| C. | received frequency by receiver |
| D. | height of ionospheric layer |
| Answer» D. height of ionospheric layer | |
| 631. |
The maximum effective aperture of a microwave antenna which has a directivity of 900, will be |
| A. | 71.619 λ2 |
| B. | 716.19 λ2 |
| C. | 7161.9 λ2 |
| D. | 71619 λ2 |
| Answer» B. 716.19 Œª2 | |
| 632. |
Waveguides are generally used above |
| A. | 20 MHz |
| B. | 100 MHz |
| C. | 200 MHz |
| D. | 1000 MHz |
| Answer» E. | |
| 633. |
The attenuation factor in parallel plane guides is given by |
| A. | a = power lost/power transmitted |
| B. | a = 2 x power lost/power transmitted |
| C. | a = power lost per unit length/2 x power transmitted |
| D. | a is always constant |
| Answer» D. a is always constant | |
| 634. |
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 | |
| 635. |
D-layer extends approximately from |
| A. | 50 to 90 km |
| B. | 20 to 50 km |
| C. | 90 to 110 km |
| D. | up to 50 km |
| Answer» B. 20 to 50 km | |
| 636. |
Troposphere is the upper part of the Earth's atmosphere which absorbs large quantities of Sun's radiations. |
| A. | 1 |
| B. | |
| C. | increases |
| D. | decreases |
| Answer» C. increases | |
| 637. |
Self impedance is |
| A. | same for transmitting (Tt) and receiving antenna (Tr) |
| B. | Tt > Tr |
| C. | Tr > Tt |
| D. | no relation |
| Answer» B. Tt > Tr | |
| 638. |
If a electromagnetic signal is incident at 0° in a waveguide then at other port of waveguide we will get |
| A. | zero power |
| B. | ‚àû power |
| C. | depend upon input signal strength |
| D. | depend on frequency |
| Answer» B. ‚àû power | |
| 639. |
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 | |
| 640. |
The radiation pattern of loop antenna is |
| A. | circle |
| B. | semicircle |
| C. | elliptical |
| D. | cardoid or Limacon |
| Answer» E. | |
| 641. |
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 | |
| 642. |
Polystyrene has a relative permittivity of 2.7. If the wave is incident at an angle θi of 30° from air into polystyrene, the angle of transmission will be nearly |
| A. | 0.2° |
| B. | 2° |
| C. | 18° |
| D. | 48° |
| Answer» D. 48¬∞ | |
| 643. |
Antenna efficiency of antenna is, if radiation resistance is 370 Ω and loss resistance is 100 Ω |
| A. | 0.8 |
| B. | 0.87 |
| C. | 0.78 |
| D. | 0.2127 |
| Answer» D. 0.2127 | |
| 644. |
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) | |
| 645. |
In case of surface waves the field strength at a point is directly proportional to |
| A. | antenna height |
| B. | wave frequency |
| C. | current of the antenna |
| D. | distance of the point from the antenna |
| Answer» E. | |
| 646. |
A waveguide behave as |
| A. | high Pass filter |
| B. | low Pass filter |
| C. | band Pass filter |
| D. | all Pass filter |
| Answer» B. low Pass filter | |
| 647. |
The force in a magnetic field is given by F = qvB |
| A. | F and q are perpendicular and v and B are perpendicular |
| B. | F and q only are perpendicular to each other |
| C. | F and v, F and B are mutually perpendicular to each other and v and B at any angle between them |
| D. | All the four components are perpendicular to each other |
| Answer» B. F and q only are perpendicular to each other | |
| 648. |
In a horizontal polarized wave |
| A. | magnetic field is perpendicular to ground |
| B. | magnetic field component is parallel to ground |
| C. | electric field component is perpendicular to ground |
| D. | electric field is parallel to ground |
| Answer» E. | |
| 649. |
Find cut off wavelength for mode TE11 in a circular waveguide having radius 2 cm. Assume K'a = 1.841 |
| A. | 4 cm |
| B. | 6.82 cm |
| C. | 8 cm |
| D. | 68.2 cm |
| Answer» C. 8 cm | |
| 650. |
VSWR can have any value between |
| A. | 0 and 1 |
| B. | - 1 to + 1 |
| C. | 0 to ‚àû |
| D. | 1 to ‚àû |
| Answer» E. | |