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MCQOPTIONS
This section includes 551 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.
| 51. |
Assertion (A): A line of length slightly more than λ/4 and open circuited at far end is equivalent to an inductive reactance.Reason (R): A line of length slightly more than λ/4 and short circuited at far end behaves as a capacitive reactance. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 52. |
The path length between ports 1 and 2 for the two waves in a hybrid ring is |
| A. | 1 |
| B. | 3λ/4 |
| C. | λ/2 |
| D. | λ/4 |
| Answer» D. λ/4 | |
| 53. |
In a rectangular waveguide cutoff wavelength for TE₁₀ mode is 8 cm. Then cutoff wavelength for TE₂₀ mode is |
| A. | 8 cm |
| B. | 6 cm |
| C. | 4 cm |
| D. | 2 cm |
| Answer» D. 2 cm | |
| 54. |
A line of length less than λ/4 and open circuited at far end behaves as |
| A. | inductance L |
| B. | capacitance C |
| C. | L and C in series |
| D. | L and C in parallel |
| Answer» C. L and C in series | |
| 55. |
A matched generator (Zg = Z0) with 1 Ω available. If all ports are matched, the power delivered at ports 1, 2, 3 respectively are |
| A. | 0.5 W, 0.5 W, 0 W |
| B. | 0 W, 0 W, 1 W |
| C. | 0.33 W each |
| D. | 0 W, 0.25 W, 0.25 W |
| Answer» B. 0 W, 0 W, 1 W | |
| 56. |
The reflection coefficient on a line is 0.2 ∠45°. The SWR is |
| A. | 0.8 |
| B. | 1.1 |
| C. | 1.2 |
| D. | 1.5 |
| Answer» E. | |
| 57. |
Assertion (A): In TE₁₀ mode the cutoff frequency of rectangular waveguide is c/2a, where a is the broad dimension and c is velocity of light.Reason (R): TE₁₀ mode is the dominant mode in rectangular waveguide. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 58. |
If D is diameter of circular waveguide the cutoff wave-length for TE₁₁ mode is equal to |
| A. | 1.706 D |
| B. | 2.11 D |
| C. | 0.82 D |
| D. | 0.41 D |
| Answer» B. 2.11 D | |
| 59. |
In TE₁₀ mode the largest electric field in a rectangular wave guide, occurs |
| A. | along centre line of broad wall (i.e. x = a/2) |
| B. | along the broad wall (i.e. x = 0 and x = a) |
| C. | either (a) or (b) |
| D. | neither (a) nor (b) |
| Answer» B. along the broad wall (i.e. x = 0 and x = a) | |
| 60. |
Consider the following statements about hybrid ring 1. Ports 1 and 2 are decoupled.2. Port 3 and 4 are coupled.3. A signal entering either port 1 or 2 splits equally between ports 3 and 4.4. A signal entering either port 3 or 4 splits equally between ports 1 and 2. Which of the above are correct? |
| A. | 1, 2, 3 and 4 |
| B. | 1, 3 and 4 |
| C. | 1 and 2 |
| D. | 2, 3 and 4 |
| Answer» C. 1 and 2 | |
| 61. |
Z₀ = (Zoc Zsc)^0.5 |
| A. | True |
| B. | False |
| C. | May be True or False |
| D. | Can't say |
| Answer» B. False | |
| 62. |
TE₁₀ mode of propagation of electromagnetic energy in waveguides can be thought of as |
| A. | three TEM waves travelling along length of wave-guide |
| B. | One TEM wave travelling along length of wave guide and one TEM wave propagation in the transverse plane |
| C. | One TEM wave travelling along the length of wave guide and two TEM waves |
| D. | none of the above |
| Answer» D. none of the above | |
| 63. |
Consider the following applications: 1. TV tuning2. Active filter3. Microwave frequency multiplication In which of above can a varactor diode be used? |
| A. | 1 2 and 3 |
| B. | l and 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» B. l and 2 only | |
| 64. |
Consider the following statements (L is the length of array between centres of end antennas and A is wave-length)1. Width of major lobe between nulls of broad side array and end fire array are different.2. Directive gain of broadside array and end fire array are different.3. Directive gain of broadside array is 4(L/λ) .Which of the above statements are correct? |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 1 only |
| D. | 1 and 3 only |
| Answer» E. | |
| 65. |
In high frequency circuits impedance matching can be done by 1. open circuited stubs2. short circuited stubs3. λ/4 transformer Which of the above correct? |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» B. 1 and 2 only | |
| 66. |
A rectangular wave guide has two stubs each of length λ/4 connected at the source end. The stubs are circuited. Then the stubs present |
| A. | an infinite impedance in shunt with line |
| B. | an infinite impedance in series with line |
| C. | a zero impedance in shunt with line |
| D. | a finite impedance in shunt with line |
| Answer» B. an infinite impedance in series with line | |
| 67. |
Consider the following applications 1. Switch2. Attenuator3. Phase shifter4. Oscillator In which of the above can a PIN diode be used? |
| A. | 1 2 3 and 4 |
| B. | 1 2 and 3 only |
| C. | 1 and 2 only |
| D. | 2, 3 and 4 only |
| Answer» C. 1 and 2 only | |
| 68. |
A line of length slightly longer than λ/4 and open circuited at far end behaves as |
| A. | inductance L |
| B. | capacitance C |
| C. | L and C in series |
| D. | L and C in parallel |
| Answer» B. capacitance C | |
| 69. |
A wave Em cos (bx - ωt) is a backward wave. |
| A. | True |
| B. | False |
| C. | May be True or False |
| D. | Can't say |
| Answer» C. May be True or False | |
| 70. |
A transmission line has Z0 = 300 Ω and ZL = (300 - j300) ohm. The transmission coefficient is |
| A. | 1.265 ∠ - 18.43° |
| B. | 1.01 ∠ - 10° |
| C. | 1.14 ∠ 66.68° |
| D. | 1.09 ∠ 66.68° |
| Answer» B. 1.01 ∠ - 10° | |
| 71. |
Consider the following statements:1. Bunching of electrons occurs in two cavity klystron amplifier.2. Bunching of electrons occurs in multi cavity klystron amplifier.3. Bunching of electrons occurs in reflex cavity klystron amplifier. Which of the above statements are correct? |
| A. | 1, 2, and only |
| B. | 1, 2 and 3 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» C. 1 and 3 only | |
| 72. |
A circular waveguide carries TE₁₁ mode whole radial electric field is given byEr = E₀j₁(r) sin Φ V/mwhere r is radial distance in cm from the axisThe cut off wavelength is |
| A. | 10 cm |
| B. | 3 π cm |
| C. | 2 π cm |
| D. | 8 cm |
| Answer» B. 3 π cm | |
| 73. |
The π mode of operation of magnetron signifies that |
| A. | the phase difference between adjacent anode poles is π radians |
| B. | the phase difference between adjacent anode poles is a multiple of π radians |
| C. | the total phase shift around the periphery is π radians |
| D. | none of the above |
| Answer» B. the phase difference between adjacent anode poles is a multiple of π radians | |
| 74. |
If in line G/C = R/L, the characteristic impedance becomes real. |
| A. | True |
| B. | False |
| C. | May be True or False |
| D. | Can't say |
| Answer» B. False | |
| 75. |
TM₀₁ mode in circular waveguide is analogous to |
| A. | TM₁₀ mode in square waveguide |
| B. | TM₁₁ mode in square waveguide |
| C. | TM₂₀ mode in square waveguide |
| D. | TM₀₂ mode in square waveguide |
| Answer» C. TM₂₀ mode in square waveguide | |
| 76. |
As compared to LED, LASER has 1. higher emission efficiency2. no tuning arrangement3. narrow spectral width4. provision for confinement Of these statements |
| A. | 1, 2, 3 are correct |
| B. | 1, 2, 4 are correct |
| C. | 1 and 3 are correct |
| D. | 1, 3, 4 are correct |
| Answer» E. | |
| 77. |
A coaxial RF cable has a characteristic impedance of 50 Ω and C equal to 40 pF/m. The inductance is |
| A. | 1 μ H/m |
| B. | 10 μ H/m |
| C. | 0.1 μ H/m |
| D. | 0.01 μ H/m |
| Answer» D. 0.01 μ H/m | |
| 78. |
If a line having Z₀ = 300 ∠ 0 W is open circuited at far end, VSWR is |
| A. | 0 |
| B. | 1 |
| C. | ∞ |
| D. | 2 |
| Answer» D. 2 | |
| 79. |
Consider the following statement: SWR of a transmission line is infinite when the load is 1. a short circuit2. a complex impedance3. an open circuit4. a pure reactance Which of the above statements are correct? |
| A. | 1 and 3 only |
| B. | 1, 2, 3 |
| C. | 2, 3, 4 |
| D. | 1, 2, 4 |
| Answer» B. 1, 2, 3 | |
| 80. |
TE₀₁ mode of propagation of electromagnetic energy |
| A. | is merely the TE₁₀ mode rotated 90° |
| B. | is merely the TE₁₀ mode rotated 180° |
| C. | is the same as TE₁₀ mode |
| D. | either (b) or (c) |
| Answer» B. is merely the TE₁₀ mode rotated 180° | |
| 81. |
A line is excited by a 100 V, 200 ohm source and is terminated by 100 Ω resistance. If the voltage on line reaches steady value in 80 ns, the natural resonant frequency is |
| A. | 100 MHz |
| B. | 50 MHz |
| C. | 12.5 MHz |
| D. | 6.25 MHz |
| Answer» D. 6.25 MHz | |
| 82. |
The following components are used to measure power output of a 2 kW TWT amplifier 1. TWT2. Low pass/High pass filter3. Low power 20 dB attenuator4. 40 dB directional coupler with matched load5. Power meter The correct sequence of connections of these components is: |
| A. | 1, 4, 2, 3, 5 |
| B. | 1, 3, 4, 2, 5 |
| C. | 1, 2, 4, 3, 5 |
| D. | 1, 4, 3, 2, 5 |
| Answer» C. 1, 2, 4, 3, 5 | |
| 83. |
A microstrip line has dielectric having relative permittivity ∈r. The effective dielectric constant is |
| A. | more than ∈r |
| B. | equal to 1 |
| C. | less than ∈r |
| D. | either a or b |
| Answer» D. either a or b | |
| 84. |
A resistive microwave load with ZL = 150 Ω is connected to 50 Ω coaxial line. SWR is |
| A. | more than 3 |
| B. | less than 3 |
| C. | equal to 3 |
| D. | either (a) or (c) |
| Answer» D. either (a) or (c) | |
| 85. |
For a rectangular waveguide having width a and height b, the cutoff wavelength for TM₁₁ mode is equal to |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 86. |
A line has Z0 = 300 ∠ 0° Ω. If ZL = 150 ∠ 0° Ω, reflection coefficient is |
| A. | 0.5 |
| B. | 0.3333 |
| C. | -0.3333 |
| D. | -0.5 |
| Answer» D. -0.5 | |
| 87. |
A loss less line of characteristic impedance Z₀ is terminated in pure reactance of -jZ₀ value. VSWR is |
| A. | 10 |
| B. | 2 |
| C. | 1 |
| D. | infinity |
| Answer» E. | |
| 88. |
A pulsed radar produces 1 μ sec pulses at a rate of 1000 per second. The duty cycle is |
| A. | 0.001 |
| B. | 0.01 |
| C. | 0.1 |
| D. | 1 |
| Answer» B. 0.01 | |
| 89. |
In a cable with ∈r = 4, the wave velocity is |
| A. | 3 x 10⁸ m/s |
| B. | 0.75 x 10⁸ m/s |
| C. | 1.5 x 10⁸ m/s |
| D. | 10⁸ m/s |
| Answer» D. 10⁸ m/s | |
| 90. |
In a klystron amplifier dc electron velocity is v₀ and dc electron charge density is ρ₀ the dc beam current is |
| A. | ρ₀v₀ |
| B. | ρ₀/v₀ |
| C. | v₀/ρ₀ |
| D. | (v₀/ρ₀)² |
| Answer» B. ρ₀/v₀ | |
| 91. |
If a line having Z₀ = 300 ∠ 0 W is short circuited at far end, VSWR is |
| A. | 0 |
| B. | 1 |
| C. | ∞ |
| D. | 2 |
| Answer» D. 2 | |
| 92. |
If ZTE is wave impedance for TE waves, Ed is maximum dielectric strength of insulating material, a and b are the width and height of a rectangular wave guide, the maximum power handling capability Pmax for TE₁₀ mode is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 93. |
If μr is relative permeability, ∈r is relative permittivity, c is velocity of light fc is cutoff frequency, phase velocity vp (i.e., speed with which a particular phase of the wave travels down a rectangular waveguide at frequency f) is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 94. |
For l |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 95. |
The Q factor of a waveguide resonator is given by (ω0 is resonant frequency, U is energy storage and WL is the power loss) |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 96. |
In a Gunn diode oscillator drift velocity of electron is 10⁷ cm/s and active region length is 10 x 10‾⁴ cm. The natural frequency of oscillation is |
| A. | 1 MHz |
| B. | 10 MHz |
| C. | 1 GHz |
| D. | 10 GHz |
| Answer» E. | |
| 97. |
Which of the following terminations makes the input impedance of a line equal to characteristic impedance Z₀? |
| A. | line open circuited at far end |
| B. | line terminated in Z₀ |
| C. | line short circuited at far end |
| D. | line terminated in inductance |
| Answer» C. line short circuited at far end | |
| 98. |
Assertion (A): In rectangular waveguide TE₀₁ mode is just TE₁₀ mode rotated by 90°.Reason (R): When a rectangular waveguide is rotated by 90°, the broad and narrow dimensions get interchanged. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» B. Both A and R are correct but R is not correct explanation of A | |
| 99. |
Assertion (A): In a power divider SH = 0, S21 = 0.707 = S3.Reason (R): In a power divider the input port (i.e., port 1) is matched and incident power is equally divided in output ports 2 and 3 |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» B. Both A and R are correct but R is not correct explanation of A | |
| 100. |
A 3 port circulator is in the given figure. Its scattering matrix is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |