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MCQOPTIONS
This section includes 248 Mcqs, each offering curated multiple-choice questions to sharpen your Electromagnetic Theory knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
Indicate which one of the following reasons for the use of an earth mat with antennas is false |
| A. | Impossibility of a good ground connection |
| B. | Provision of an earth for the antenna |
| C. | Protection of personnel working underneath |
| D. | Improvement of the radiation pattern of the antenna |
| Answer» D. Improvement of the radiation pattern of the antenna | |
| 102. |
Compared with equivalent transmission lines, 3-GHz waveguides (indicate false statement) |
| A. | Are less lossy |
| B. | Can carry higher powers |
| C. | Are less bulky |
| D. | Have lower attenuation |
| Answer» D. Have lower attenuation | |
| 103. |
One of the following consists of nonresonant antennas |
| A. | The rhombic antenna |
| B. | The folded dipole |
| C. | The end-fire array |
| D. | The broadside array |
| Answer» B. The folded dipole | |
| 104. |
Helical antennas are often used for satellite tracking at VHF because of |
| A. | Troposcatter |
| B. | Superrefraction |
| C. | Ionospheric refraction |
| D. | The Faraday effect |
| Answer» E. | |
| 105. |
Electromagnetic waves are refracted when they |
| A. | Pass into a medium of different dielectric constant |
| B. | Are polarized at right angles to the direction of propagation |
| C. | Encounter a perfectly conducting surface |
| D. | Pass through a small slot in a conducting plane |
| Answer» B. Are polarized at right angles to the direction of propagation | |
| 106. |
Medium 1 has the electrical permittivity |
| A. | (2 ux 7.5 uy + 2.5 uz) V/m |
| B. | (2 ux 2 uy 0.6 uz) V/m |
| C. | (1.2 ux 3 uy + 1 uz) V/m |
| D. | (1.2 ux 2 uy + 0.6 uz) V/m |
| Answer» D. (1.2 ux 2 uy + 0.6 uz) V/m | |
| 107. |
An antenna has a power input of 40 watts and a efficiency of 90%. The radiation intensity has to have a max of 150 W/unit solid angle. Directivity |
| A. | 13.5 |
| B. | 16.67 |
| C. | 1.333 |
| D. | 1.0748 |
| Answer» C. 1.333 | |
| 108. |
The dominant mode of propagation is preferred with rectangular waveguides because (indicate false statement) |
| A. | It leads to the smallest waveguide dimensions |
| B. | The resulting impedance can be matched directly to coaxial lines |
| C. | It is easier to excite than the other modes |
| D. | Propagation of it without any spurious generation can be ensured |
| Answer» C. It is easier to excite than the other modes | |
| 109. |
Calculate the front-to-back ratio of an antenna in dB which radiates 3 kW in its most optimum direction and 500 watts in the opposite direction |
| A. | 0.782 |
| B. | 7.782 |
| C. | 22.22 |
| D. | None of these |
| Answer» C. 22.22 | |
| 110. |
A thin dipole antenna is /15 metre long. If Its loss resistance is 1.5 . Find radiation resistance and efficiency |
| A. | Rr = 35 , = 80% |
| B. | Rr = 3.5 , = 70% |
| C. | Rr = 3.5 , = 80% |
| D. | Rr = 7.0 , = 70% |
| Answer» C. Rr = 3.5 , = 80% | |
| 111. |
A uniform plane wave travelling in air is incident on the plane boundary between air and another dielectric medium with |
| A. | 0 |
| B. | 0.5 180 |
| C. | 0.333 0 |
| D. | 0.333 180 |
| Answer» E. | |
| 112. |
8-point charges of 1 nc each are located at the corners of a cube in free space that is 1 m on a side, then |
| A. | 0 V/m |
| B. | 5 V/m |
| C. | 4 V/m |
| D. | 5 V/m |
| Answer» B. 5 V/m | |
| 113. |
A plane wave is characterised by this wave is |
| A. | Linearly polarized |
| B. | Circularly polarized |
| C. | Elliptically polarized |
| D. | Unpolarized |
| Answer» C. Elliptically polarized | |
| 114. |
The phase velocity for the TE |
| A. | Less than C |
| B. | Equal to C |
| C. | Greater than C |
| D. | None of these |
| Answer» D. None of these | |
| 115. |
In an impedance smith chart a clockwise movement along a constant resistance circle gives rise to |
| A. | A decrease in the value of reactance |
| B. | An increase in the value of reactance |
| C. | No change in the reactance value |
| D. | No change in the impedance value |
| Answer» C. No change in the reactance value | |
| 116. |
The line of sight communication requires the transmit and receive antenna to face each other. If the transmit antenna is vertically polarized for 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» C. At 45 with respect to horizontal polarization | |
| 117. |
In a uniform linear array four isotropic radiating elements are spaced /4 apart. The progressive phase shift between the elements required for forming the main beam at 60 off the end fire is |
| A. | radians |
| B. | /2 radians |
| C. | /4 radians |
| D. | /8 radians |
| Answer» D. /8 radians | |
| 118. |
A medium wave radio transmitter operating at a wavelength of 492 m has a lower antenna height 124 m. What is the radiation resistance of the antenna? |
| A. | 25 |
| B. | 36.5 |
| C. | 50 |
| D. | 73 |
| Answer» B. 36.5 | |
| 119. |
An uniform plane wave incident normally on a plane surface of dielectric material is reflected with a VSWR of 3 what is the percentage of incident power that is reflected? |
| A. | 10% |
| B. | 25% |
| C. | 50% |
| D. | 75% |
| Answer» C. 50% | |
| 120. |
A material has conductivity of 10 |
| A. | 45 MHz |
| B. | 90 MHz |
| C. | 450 MHz |
| D. | 900 MHz |
| Answer» B. 90 MHz | |
| 121. |
The phase velocity of wave propagating in a hollow metal waveguide is |
| A. | Greater than the velocity of light in free space |
| B. | Less than the velocity of light in free space |
| C. | Equal to the velocity of light in free space |
| D. | Equal to the group velocity |
| Answer» B. Less than the velocity of light in free space | |
| 122. |
If a plane electromagnetic wave satisfies the equation |
| A. | x-direction |
| B. | z-direction |
| C. | y-direction |
| D. | xy plane at an angle of 45 between x and z direction |
| Answer» C. y-direction | |
| 123. |
A transmission line is distortionless if |
| A. | <table><tr><td rowspan="2">RL = </td> <td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">GC</td></tr></table> |
| B. | |
| C. | RL = GC |
| D. | LG = RC |
| E. | RG = LC |
| Answer» E. RG = LC | |
| 124. |
A rectangular waveguide has dimensions 1 cm 0.5 cm its cut-off frequency is |
| A. | 5 GHz |
| B. | 10 GHz |
| C. | 15 GHz |
| D. | 20 GHz |
| Answer» D. 20 GHz | |
| 125. |
For an 8 feet (2.4 m) parabolic dish antenna operating at 4 GHz the minimum distance required for the far field measurement is closest to |
| A. | 7.5 cm |
| B. | 15 cm |
| C. | 15 m |
| D. | 150 m |
| Answer» E. | |
| 126. |
If the diameter of a /2 dipole antenna is increased from /100 to /50 then its |
| A. | Bandwidth increases |
| B. | Bandwidth decreases |
| C. | Gain increases |
| D. | Gain decreases |
| Answer» B. Bandwidth decreases | |
| 127. |
A-TEM wave incident normally upon a perfect conductor the E and H fields at the boundary will be respectively |
| A. | Minimum and minimum |
| B. | Maximum and maximum |
| C. | Minimum and maximum |
| D. | Maximum and minimum |
| Answer» E. | |
| 128. |
The velocity of the plane wave e |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2 </center></td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> </center></td></tr><tr><td style="text-align: center;">2b</td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> <sup>2</sup></center></td></tr><tr><td style="text-align: center;"> <sup>2</sup></td></tr></table> |
| D. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> </center></td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| Answer» E. | |
| 129. |
The frequency of the power wave associated with an electromagnetic wave having an E field as |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> </center></td></tr><tr><td style="text-align: center;">8 </td></tr></table> |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> </center></td></tr><tr><td style="text-align: center;">4 </td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> </center></td></tr><tr><td style="text-align: center;">2 </td></tr></table> |
| D. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> </center></td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| Answer» E. | |
| 130. |
A plane electromagnetic wave in free space is specified by the electric field |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>a<sub>y</sub> </center></td><td rowspan="2">[20 cos ( t + z) + 5 cos ( t + z)] A/m <br></td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>a<sub>y</sub> </center></td><td rowspan="2">[20 cos ( t + z) 5 cos ( t + z)] A/m <br></td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>a<sub>y</sub> </center></td><td rowspan="2">[20 cos ( t z) + 5 cos ( t + z)] A/m <br></td></tr><tr><td style="text-align: center;">120 </td></tr></table> |
| D. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>a<sub>y</sub> </center></td><td rowspan="2">[20 cos ( t z) 5 cos ( t + z)] A/m <br></td></tr><tr><td style="text-align: center;">120 </td></tr></table> |
| Answer» D. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>a<sub>y</sub> </center></td><td rowspan="2">[20 cos ( t z) 5 cos ( t + z)] A/m <br></td></tr><tr><td style="text-align: center;">120 </td></tr></table> | |
| 131. |
Two infinite parallel metal plates are charged with equal surface charge density of the same polarity. The electric field in the gap between the plates is |
| A. | The same as that produced by one plate |
| B. | Double of the field produced by one plate |
| C. | Dependent on coordinates of field point |
| D. | Zero |
| Answer» E. | |
| 132. |
Consider the following statements regarding field boundary conditions: |
| A. | 1, 2 and 3 are correct |
| B. | 2, 3 and 4 are correct |
| C. | 1, 2 and 4 are correct |
| D. | 1, 3 and 4 are correct |
| Answer» E. | |
| 133. |
The energy stored in the magnetic field of a solenoid 30 cm long and 3 cm diameter wound with 1000 turns of wire carrying a current of 10 A is |
| A. | 0.015 joule |
| B. | 0.15 joule |
| C. | 0.5 joule |
| D. | 1.15 joule |
| Answer» C. 0.5 joule | |
| 134. |
If V, w, q stand for voltage, energy and charge, then V can be expressed as |
| A. | <table><tr><td rowspan="2">V = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>dq</center></td></tr><tr><td style="text-align: center;">dw</td></tr></table> |
| B. | <table><tr><td rowspan="2">V = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>dw</center></td></tr><tr><td style="text-align: center;">dq</td></tr></table> |
| C. | |
| D. | <table><tr><td rowspan="2">dV = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>dw</center></td></tr><tr><td style="text-align: center;">dq</td></tr></table> |
| E. | <table><tr><td rowspan="2">dV = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>dq</center></td></tr><tr><td style="text-align: center;">dw</td></tr></table> |
| Answer» C. | |
| 135. |
The velocity of electromagnetic waves in free space |
| A. | Increases with increase of frequency |
| B. | Decreases with increase of frequency |
| C. | Is independent of frequency |
| D. | May increase or decrease with increase of frequency |
| Answer» D. May increase or decrease with increase of frequency | |
| 136. |
The value of ∮ di along a circle of radius 2 units is |
| A. | Zero |
| B. | 2 |
| C. | 4 |
| D. | 8 |
| Answer» B. 2 | |
| 137. |
If the vectors |
| A. | <table><tr><td> </td><td> </td></tr><tr><td>A </td><td>B is solenoidal</td></tr></table> |
| B. | <table><tr><td> </td><td> </td></tr><tr><td>A </td><td>B is conservative</td></tr></table> |
| C. | <table><tr><td> </td><td> </td></tr><tr><td>A + </td><td>B is solenoidal</td></tr></table> |
| D. | <table><tr><td> </td><td> </td></tr><tr><td>A </td><td>B is solenoidal</td></tr></table> |
| Answer» B. <table><tr><td> </td><td> </td></tr><tr><td>A </td><td>B is conservative</td></tr></table> | |
| 138. |
The magnitude of open circuit and short circuit input impedances of a transmission line are 100 and 25 respectively the characteristic impedance of the line is |
| A. | 25 |
| B. | 50 |
| C. | 75 |
| D. | 100 |
| Answer» C. 75 | |
| 139. |
Poynting vector signifies |
| A. | Current density vector producing electrostatic field |
| B. | Power density vector producing electromagnetic field |
| C. | Current density vector producing electromagnetic field |
| D. | Power density vector producing electrostatic field |
| Answer» C. Current density vector producing electromagnetic field | |
| 140. |
Which one of the following sets of equations is independent in Maxwell's equations? |
| A. | The two curl equations |
| B. | The two divergence equations |
| C. | Both the curl and divergence equations |
| D. | The two curl equations combined with the continuity equation |
| Answer» D. The two curl equations combined with the continuity equation | |
| 141. |
Consider a transmission line of characteristics impedance 50 ohm. Let it be terminated at one end by + j 50 ohm. The VSWR produced by it in the transmission line will be |
| A. | + 1 |
| B. | 0 |
| C. | |
| D. | + j |
| Answer» D. + j | |
| 142. |
Inside a hollow conducting sphere |
| A. | Electric field is zero |
| B. | Electric field is a non-zero constant |
| C. | Electric field changes with the magnitude of the charge given to the conductor |
| D. | Electric field changes with distance from the centre of the sphere |
| Answer» B. Electric field is a non-zero constant | |
| 143. |
UHF and microwaves in the frequency range 300 MHz to 30 GHz can be best transmitted using |
| A. | Ground wave propagation |
| B. | Duct propagation |
| C. | Sky wave propagation |
| D. | None of the above |
| Answer» C. Sky wave propagation | |
| 144. |
An air filled rectangular waveguide has dimensions 6 cm, 4 cm. The cut-off frequency for TE |
| A. | 2.5 GHz |
| B. | 25 gHz |
| C. | 25 MHz |
| D. | 5 GHz |
| Answer» B. 25 gHz | |
| 145. |
A transverse electromagnetic wave with circular polarization is received by a dipole antenna. Due to polarization mismatch, the power transfer efficiency from the wave to the antenna is reduced to about |
| A. | 50% |
| B. | 33.3% |
| C. | 25% |
| D. | 0% |
| Answer» B. 33.3% | |
| 146. |
A magnetic field |
| A. | <table><tr><td> </td><td> </td><td> </td><td> </td></tr><br><tr><td>E = v<sub>0</sub>(3</td><td>a<sub>x</sub> 2</td><td>a<sub>y</sub> 4</td><td>a<sub>z</sub>)</td></tr></table> |
| B. | <table><tr><td> </td><td> </td><td> </td></tr><br><tr><td>E = v<sub>0</sub>(14</td><td>a<sub>y</sub> &plus; 7</td><td>a<sub>z</sub>)</td></tr></table> |
| C. | <table><tr><td> </td><td></td><td></td><td> </td><td> </td></tr><br><tr><td>E = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>v<sub>0</sub></center></td><td>(14</td><td>a<sub>y</sub> &plus; 7</td><td>a<sub>z</sub>)</td></tr><tr><td></td><td style="text-align: center;"> </td></tr></table> |
| D. | <table><tr><td> </td><td></td><td></td><td> </td><td> </td></tr><br><tr><td rowspan="2">E = &plus;</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>v<sub>0</sub></center></td><td>(14</td><td>a<sub>y</sub> &plus; 7</td><td>a<sub>z</sub>)</td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| Answer» C. <table><tr><td> </td><td></td><td></td><td> </td><td> </td></tr><br><tr><td>E = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>v<sub>0</sub></center></td><td>(14</td><td>a<sub>y</sub> &plus; 7</td><td>a<sub>z</sub>)</td></tr><tr><td></td><td style="text-align: center;"> </td></tr></table> | |
| 147. |
The ratio of the radii required to give a 60 ohm coaxial line filled with PTFE of |
| A. | 4.1: 1 |
| B. | 3.25: 1 |
| C. | 1: 1 |
| D. | 7.39: 1 |
| Answer» B. 3.25: 1 | |
| 148. |
The characteristic impedance of a coaxial cable depends on: |
| A. | 3 and 4 |
| B. | 2 and 3 |
| C. | 1, 3, 4 |
| D. | 4 only |
| Answer» E. | |
| 149. |
A circular loop has its radius increasing at a rate of 2 m/s. The loop is placed perpendicular to a constant magnetic field 0.1 Wb/m2. When the radius of the loop is 2 m, the emf induced in the loop will be |
| A. | 0.8 V |
| B. | 0.04 V |
| C. | 0.2 V |
| D. | Zero |
| Answer» B. 0.04 V | |
| 150. |
Given that L = 1 H/m, C = 11.11 pf/m the group delay time is |
| A. | Nil |
| B. | 0.33 n sec |
| C. | 0.3 sec |
| D. | 33 sec |
| Answer» C. 0.3 sec | |