Explore topic-wise MCQs in Engineering.

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.

1501.

If the height of transmitting and receiving antenna in a LOS system are 49 meter and a 9 meter respectively then the distance up to which communication may be possible is about

A. 40 km
B. 110 km
C. 400 km
D. 1100 km
Answer» B. 110 km
Discussion
1502.

In a line VSWR of a load is 6 dB. The reflection coefficient will be

A. 0.033
B. 0.33
C. 0.66
D. 3.3
Answer» D. 3.3
Discussion
1503.

The refractive index of E layer at frequency of 81 N

A. 0
B.
C. 1
D. 0.5
Answer» B.
Discussion
1504.

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
Discussion
1505.

An alternating current or voltage is that which

A. changes in magnitude only
B. changes in direction only
C. both (a) and (b)
D. has a random movement of electrons
Answer» D. has a random movement of electrons
Discussion
1506.

When the magnetic vector is parallel to the boundary surface and electric vector is parallel to the place of incidence, the polarization is

A. zero
B. vertical
C. perpendicular
D. horizontal
Answer» C. perpendicular
Discussion
1507.

The troposphere extends from earth surface to a height of

A. 15 km
B. 90 km
C. 150 km
D. 200 km
Answer» B. 90 km
Discussion
1508.

Antenna reciprocity is put to use in

A. radar system
B. commercial broadcast
C. TV broadcast system
D. none of the above
Answer» B. commercial broadcast
Discussion
1509.

For satellite communication, the frequency should be

A. equal to the critical frequency
B. more than the critical frequency
C. less than the critical frequency
D. none of these
Answer» C. less than the critical frequency
Discussion
1510.

For an elliptically polarized wave incident on the interface of a dielectric at the Brewster angle the reflected wave will be

A. elliptically polarized
B. linearly polarized
C. right circularly polarized
D. left circularly polarized
Answer» B. linearly polarized
Discussion
1511.

Which of the antenna is best excited by a waveguide?

A. Horn
B. Discone
C. Helical
D. Biconical
Answer» B. Discone
Discussion
1512.

An end fire array consisting of several half-wave lengths of directive gain 40, then array length will be

A. 10
B. 100
C. 20
D. 5
Answer» B. 100
Discussion
1513.

Loop antennas are mostly employed for direction finding (DF) purposes because they are small and hence portable.

A. True
B. False
Answer» B. False
Discussion
1514.

The velocity of electromagnetic wave in free space is given by

A. <span class="root"> <sub>0</sub>/ <sub>0</sub></span>
B. <span class="root"> <sub>0</sub> . <sub>0</sub></span>
C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/211-597-1.png">
D. <span class="root"> <sub>0</sub>/ <sub>0</sub></span>
Answer» D. <span class="root"> <sub>0</sub>/ <sub>0</sub></span>
Discussion
1515.

Surface integral of the electric field intensity is

A. differential of volume flux
B. electrical charge
C. net flux emanating from the surface
D. none of the above
Answer» D. none of the above
Discussion
1516.

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
Discussion
1517.

Directivity gain depends on

A. the distribution of radiated power in space
B. solid angle of the radiated field pattern
C. both (a) and (b)
D. none of the above
Answer» B. solid angle of the radiated field pattern
Discussion
1518.

The input impedance for a half dipole if radii of both the antenna is 4 and 8 meter respectively

A. 600 &ohm;
B. 100 &ohm;
C. 657 &ohm;
D. 650 &ohm;
Answer» D. 650 &ohm;
Discussion
1519.

The fluctuation in the received signal strength at the receiver of a random variation in the received signal is known as

A. fluctuation
B. fading
C. absorption
D. cycling
Answer» C. absorption
Discussion
1520.

End fire coupler is formed

A. when two equal radiators are operated in phase quadrature at a distance of /4 apart
B. when two equal radiators are operated in parallel at a distance of /4 apart
C. when two equal radiators are operated in phase quadrature at a distance of /2 apart
D. none of the above
Answer» B. when two equal radiators are operated in parallel at a distance of /4 apart
Discussion
1521.

Calculate cut off frequency for dominant mode in rectangular waveguide if dimensions are a = 2, b = 1 cm.

A. 7.5 GHz
B. 1.5 GHz
C. 15 GHz
D. 150 GHz
Answer» B. 1.5 GHz
Discussion
1522.

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
Discussion
1523.

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.
Discussion
1524.

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
Discussion
1525.

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
Discussion
1526.

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
Discussion
1527.

The sinusoidally time varying vector field is

A. elliptically polarized
B. circularly polarized
C. linearly polarized
D. unpolarized
Answer» E.
Discussion
1528.

Gain of an antenna with a circular aperture of diameter 4 meter at frequency of 10 GHz, with directivity 60

A. 60
B. 100
C. 30
D. 90
Answer» B. 100
Discussion
1529.

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
Discussion
1530.

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
Discussion
1531.

Medium 1 has the electrical permittivity 1 = 1.5 0 farad/m and occupies the region to the left of x = 0 plane. Medium 2 has the electrical permittivity 2 = 2.5 0 farad/m and the occupies the region to the right of x = 0 plane. If E1 in medium 1 is volt/m, then E2 in medium 2 is

A. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-215-2.png">
B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-215-3.png">
C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-215-5.png">
D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-215-4.png">
Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-215-4.png">
Discussion
1532.

Polarization of a wave is

A. direction of electric field
B. direction of magnetic field at some fixed point in space
C. either (a) or (b)
D. none of the above
Answer» B. direction of magnetic field at some fixed point in space
Discussion
1533.

For a transmission line with homogeneous dielectric the capacitance per unit length is 'c', the relative permittivity of the dielectric is ' r' and velocity of light in free space is 'v' the characteristic impedance z0 is equal to

A. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/197-254-1.png">
B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/197-254-2.png">
C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/197-254-3.png">
D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/197-254-4.png">
Answer» D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/197-254-4.png">
Discussion
1534.

If and the time average Poynting vector is

A. null vector
B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-223-3.png">
C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-223-4.png">
D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-223-5.png">
Answer» B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/195-223-3.png">
Discussion
1535.

The I/P impedance of a short circuited quarter wave long transmission line is

A. purely reactive
B. purely resistive
C. depend on the characteristic impedance of the line
D. none of the above
Answer» E.
Discussion
1536.

A dipole antenna of /8 length has an equivalent total loss resistance of 1.5 &amp;ohm;. The efficiency of the antenna is

A. 0.89159%
B. 8.9159%
C. 89.159%
D. 891.59%
Answer» D. 891.59%
Discussion
1537.

A uniform plane wave travelling in air is incident on the plane boundary between air and another dielectric medium with r = 4. The reflection coefficient for the normal incidence is

A. zero
B. 0.5 180
C. 0.33 0
D. 0.33 180
Answer» E.
Discussion
1538.

A 10 GHz signal propagates in a waveguide with a phase velocity of 4 x 108 m/s. If the signal produces standing wave in the guide, then the distance between successive minimal will be

A. 10 mm
B. 20 mm
C. 30 mm
D. 40 mm
Answer» C. 30 mm
Discussion
1539.

The distance between maxima and minima of a standing wave is

A. /4
B. /2
C.
D. 2
Answer» B. /2
Discussion
1540.

The incidence from dielectric medium 1 ( 1) into dielectric medium 2 ( 2), Brewster angle B and the corresponding angle of transmission t for will be respectively

A. 30 and 30
B. 30 and 60
C. 60 and 30
D. 30 and 60
Answer» D. 30 and 60
Discussion
1541.

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
Discussion
1542.

A vertical wire of 1 meter length carries a current of 1 A at 10 MHz. The total radiated power is nearly

A. 0.13 W
B. 0.88 W
C. 7.3 W
D. 73 W
Answer» E.
Discussion
1543.

For a reflection co-efficient of 0.5, the value of SWR is

A. -1
B. 1
C. 2
D. 3
Answer» E.
Discussion
1544.

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
Discussion
1545.

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
Discussion
1546.

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
Discussion
1547.

Voltage standing wave pattern in a loss less transmission line with characteristic impedance 50 &amp;ohm; and a resistive load is shown in the figure. The value of load resistance is

A. 50 &ohm;
B. 200 &ohm;
C. 12.5 &ohm;
D. 0 &ohm;
Answer» C. 12.5 &ohm;
Discussion
1548.

1 dB is equal to __________ nepier

A. 8.6
B. 6.8
C. 8
D. 0
Answer» B. 6.8
Discussion
1549.

Cassergain feed is used with a parabolic reflector to

A. increase the gain of the system
B. increase the beamwidth of the system
C. reduce the size of the main reflector
D. allow the feed to be placed at a convenient point
Answer» E.
Discussion
1550.

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
Discussion