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.

1251.

VSWR can have any value between

A. 0 and 1
B. - 1 to + 1
C. 0 to
D. 1 to
Answer» E.
Discussion
1252.

Refraction of electromagnetic waves occurs when they

A. pass through a small slot in a conducting plane
B. pass into a medium of different dielectric constant
C. are polarized at right angles to the direction of propagation
D. encounter a perfectly conduction surface
Answer» B. pass into a medium of different dielectric constant
Discussion
1253.

The impedance inversion may be objected with

A. a short-circuited stub
B. an open-circuited stub
C. a half-wave line
D. a quarter-wave line
Answer» E.
Discussion
1254.

An electromagnetic wave incidents on a perfect insulator at an angle. If the wave is not entirely parallel polarized, then

A. the reflected wave will be entirely polarized parallel to the plane of incidence
B. there will be no reflection
C. the reflected wave will be entirely polarized perpendicular to the plane of incidence
D. any of the above
Answer» D. any of the above
Discussion
1255.

Coaxial cables can be used for which frequency?

A. 15 kHz
B. 10 MHz
C. 200 MHz
D. 2000 MHz
Answer» D. 2000 MHz
Discussion
1256.

The "boundary sphere" between antenna region and free space region appears to "opaque"

A. along the dipole axis
B. along perpendicular direction
C. along the dipole axis as well as perpendicular direction
D. neither along the dipole axis nor along the perpendicular direction
Answer» B. along perpendicular direction
Discussion
1257.

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.
Discussion
1258.

Surface waves can propagate on Piezoelectric substrates.

A. True
B. False
Answer» B. False
Discussion
1259.

Brewster angle is the angle for which there is

A. no reflection and the incident wave is vertically polarized
B. reflection and the incident wave is horizontally polarized
C. no reflection and the incident wave is horizontally polarized
D. none of the above
Answer» B. reflection and the incident wave is horizontally polarized
Discussion
1260.

For an antenna radiation and induction fields are

A. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-327-1.png">
B. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-327-2.png">
C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-327-3.png">
D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-327-4.png">
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/200-327-3.png">
Discussion
1261.

Which one is not correct for folded dipole antenna?

A. High I/P impedance
B. Low I/P impedance
C. High bandwidth
D. Used as reactance compensation network
Answer» C. High bandwidth
Discussion
1262.

For VLF antennas radiation resistance is usually of the order of

A. less than one ohm
B. 13 to 20 ohms
C. around 100 ohms
D. more than 200 ohms
Answer» B. 13 to 20 ohms
Discussion
1263.

Which of the following relations is incorrect?

A. mmf x reluctance = 1
B. conductance x resistance = 1
C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/192-142-1.png">
D. none of the above
Answer» B. conductance x resistance = 1
Discussion
1264.

An antenna array pattern is to used for increasing

A. gain
B. directivity
C. directive gain
D. all
Answer» E.
Discussion
1265.

End fire array is called a linear resonant dipole array.

A. True
B. False
Answer» B. False
Discussion
1266.

Which of the following statements is incorrect regarding Balun transformer?

A. It changes impedance like current transformer
B. It changes balanced to unbalanced line
C. It is used to couple a co-axial line to a parallel line wire
D. Any of the above
Answer» B. It changes balanced to unbalanced line
Discussion
1267.

The maximum usable frequency for the 'E' layer is 10 MHz.

A. True
B. False
Answer» B. False
Discussion
1268.

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.
Discussion
1269.

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.
Discussion
1270.

Radiation resistance of half-wave dipole ( /2) antenna is in free space

A. 73 &ohm;
B. 120
C. <span class="symbol">p</span>
D. 36.5 &ohm;
E. 70 &ohm;
Answer» B. 120
Discussion
1271.

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
Discussion
1272.

The ratio of tangential component of electric field at the surface of a conductor and the linear current density resulting from this field is __________ impedance

A. characteristic
B. critical
C. surface
D. polarizing
Answer» D. polarizing
Discussion
1273.

The gain of collinear arrays is maximum when the spacing between the elements is

A. 0.1 to 0.3
B. 0.3 to 0.9
C. 0.5 to 0.7
D. 0.7 to 0.9
Answer» C. 0.5 to 0.7
Discussion
1274.

Virtual height of an ionospheric layer is always greater than its actual height.

A. True
B. False
Answer» B. False
Discussion
1275.

The duration of sunspot cycle is

A. 1 year
B. 11 years
C. 55 years
D. 100 years
Answer» C. 55 years
Discussion
1276.

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.
Discussion
1277.

Ground wave propagation is useful for

A. microwave
B. medium wave
C. short wave
D. long distance
Answer» C. short wave
Discussion
1278.

The effective height of a vertical radiator can be increased by

A. loading with lumped inductance
B. supporting on an insulator
C. capacitive loading
D. giving input more power
Answer» D. giving input more power
Discussion
1279.

An antenna has 40 &amp;ohm; resistance and 60 &amp;ohm; radiation resistance. The efficiency of the antenna is

A. 30%
B. 40%
C. 50%
D. 60%
Answer» E.
Discussion
1280.

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
Discussion
1281.

In a four element Yagi-Uda antenna

A. there is one driven element, one director and two reflectors
B. there is one driven element, two directors and one reflector
C. there are two driven elements, one director and two reflectors
D. all the 4 elements are driven element
Answer» C. there are two driven elements, one director and two reflectors
Discussion
1282.

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
Discussion
1283.

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
Discussion
1284.

In waveguide Degenerate modes are

A. two mode having same cut off frequency
B. two mode having same power
C. two mode having same phase velocity
D. it is a hypothetical mode
Answer» B. two mode having same power
Discussion
1285.

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.
Discussion
1286.

The directive gain of /2 resonant wire is 1.64.

A. True
B. False
Answer» B. False
Discussion
1287.

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
Discussion
1288.

Microwave signals follow the curvature of the earth and the phenomenon is known as

A. tropospheric scatter
B. duct propagation
C. Faraday effect
D. none of the above
Answer» C. Faraday effect
Discussion
1289.

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
Discussion
1290.

Induction and radiation fields are equal at a distance equal to

A. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/210-569-1.png">
B. 6
C. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/210-569-2.png">
D. <img src="/_files/images/electronics-and-communication-engineering/electromagnetic-field-theory/210-569-3.png">
Answer» E.
Discussion
1291.

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
Discussion
1292.

A long periodic antenna is a

A. frequency independent antenna
B. frequency dependent antenna
C. directional antenna
D. none of the above
Answer» B. frequency dependent antenna
Discussion
1293.

Electromagnetic cavity resonators (energy storage devices) are used in

A. wave meters
B. bandpass filters
C. high frequency tubes
D. all of the above
Answer» E.
Discussion
1294.

Waveguides are generally used above

A. 20 MHz
B. 100 MHz
C. 200 MHz
D. 1000 MHz
Answer» E.
Discussion
1295.

Which type of fading causes serious distortion of modulated signal?

A. Selective fading
B. Interference fading
C. Absorption fading
D. Polarization fading
Answer» B. Interference fading
Discussion
1296.

The term __________ applies to troposcatter propagation

A. fading
B. Faraday rotation
C. SIDS
D. atmospheric storms
Answer» C. SIDS
Discussion
1297.

In waveguides the existing waves are

A. TE only
B. TM only
C. both (a) and (b)
D. all of the above
Answer» E.
Discussion
1298.

So-called 'grounded' antennas are often found insulated from the ground electrically.

A. True
B. False
Answer» B. False
Discussion
1299.

A folded dipole antenna is conveniently connected to

A. shielded line
B. two wire line
C. coaxial line
D. flat ribbon type transmission line
Answer» E.
Discussion
1300.

Broadcasting antennas are generally

A. omnidirectional type
B. vertical type
C. horizontal type
D. helical
Answer» C. horizontal type
Discussion