MCQOPTIONS
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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.
| 451. |
Slotted line can be used for measurement of high frequencies |
| A. | 1 |
| B. | |
| C. | air |
| D. | magnetic material |
| Answer» B. | |
| 452. |
A microwave connector should have high SWR. |
| A. | 1 |
| B. | |
| C. | Both A and R are correct and R is correct explanation of A |
| D. | Both A and R are correct but R is not correct explanation of A |
| Answer» C. Both A and R are correct and R is correct explanation of A | |
| 453. |
The semiconductor diode which can be used in switching circuit in microwave range is |
| A. | PIN diode |
| B. | Varactor diode |
| C. | Tunnel diode |
| D. | Gunn diode |
| Answer» B. Varactor diode | |
| 454. |
To couple a coaxial line to a parallel wire line it is best to use |
| A. | slotted line |
| B. | balun |
| C. | directional coupler |
| D. | λ/4 transformer |
| Answer» C. directional coupler | |
| 455. |
In microwave circuits, a mode transducer is used to |
| A. | change mode of wave transmission |
| B. | change direction of wave transmission |
| C. | change polarization of wave transmission |
| D. | change mode, direction or polarization wave transmission |
| Answer» E. | |
| 456. |
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¬∞ | |
| 457. |
A reflex klystron oscillator is a |
| A. | low power device |
| B. | high power device |
| C. | high efficiency device |
| D. | both (a) and (b) |
| Answer» B. high power device | |
| 458. |
In a TWT the amplitude of resultant wave travelling down the helix remains constant |
| A. | 1 |
| B. | |
| C. | 0.45 A |
| D. | 0.3 A |
| Answer» C. 0.45 A | |
| 459. |
In Reflex Klystron oscillator the focussing electrode is at a high potential |
| A. | 1 |
| B. | |
| Answer» C. | |
| 460. |
A waveguide twist is used to change the plane of polarization. |
| A. | 1 |
| B. | |
| C. | 1 and 2 only |
| D. | 3 and 4 only |
| Answer» B. | |
| 461. |
For a 50 Ω resistor for 3 GHz application, the stray capacitance should be less than |
| A. | 1 μF |
| B. | 1 nF |
| C. | 1 pF |
| D. | 0.1 pF |
| Answer» E. | |
| 462. |
Which mode is called dominant mode in rectangular wave guide? |
| A. | TE01 |
| B. | TE11 |
| C. | TE10 |
| D. | TE20 |
| Answer» D. TE20 | |
| 463. |
The frequency of oscillation in a backward wave oscillator can be changed by |
| A. | varying the voltage which controls beam velocity |
| B. | varying the beam current |
| C. | both by varying the beam current and by light varying the voltage which controls beam velocity |
| D. | changing the rate of thermionic emission |
| Answer» B. varying the beam current | |
| 464. |
A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then |
| A. | there will be no oscillations on line |
| B. | there will be only 1 or 2 oscillations on line |
| C. | there will be a finite number of oscillations on line |
| D. | the oscillations will continue indefinitely |
| Answer» E. | |
| 465. |
When resonant cavities are coupled together the result is |
| A. | one resonant frequency |
| B. | n resonant frequencies |
| C. | resonant frequencies |
| D. | either (b) or (c) |
| Answer» C. resonant frequencies | |
| 466. |
A coaxial line has L = 500 nH/m and C = 50 pF/m. The characteristic impedance is |
| A. | 500 Ω |
| B. | 250 Ω |
| C. | 100 Ω |
| D. | 50 Ω |
| Answer» D. 50 Œ© | |
| 467. |
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 | |
| 468. |
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 | |
| 469. |
Most electromagnetic transmission in rectangular wave-guide uses |
| A. | TE10 mode |
| B. | TE01 mode |
| C. | TE20 mode |
| D. | TE11 mode |
| Answer» B. TE01 mode | |
| 470. |
A quarter wave line open circuited at far end behaves as |
| A. | inductance |
| B. | L and C in parallel |
| C. | capacitance |
| D. | L and C in series |
| Answer» E. | |
| 471. |
The fabrication of microstrip line is done by |
| A. | photo etching |
| B. | printed circuit technique |
| C. | oxidation |
| D. | cladding |
| Answer» C. oxidation | |
| 472. |
Atomic and molecular resonance is observed in many substances |
| A. | at microwave frequencies |
| B. | at low frequencies |
| C. | at frequencies used in AM broadcast |
| D. | at both (b) and (c) |
| Answer» B. at low frequencies | |
| 473. |
The usable bandwidth of ridge wave guide |
| A. | is lower than that of rectangular waveguide |
| B. | is higher than that of rectangular waveguide |
| C. | is almost same as that of rectangular waveguide |
| D. | is very small as compared to that of rectangular waveguide |
| Answer» C. is almost same as that of rectangular waveguide | |
| 474. |
If a line having Z0 = 300 ∠ 0 W is open circuited at far end, VSWR is |
| A. | 0 |
| B. | 1 |
| C. | ‚àû |
| D. | 2 |
| Answer» D. 2 | |
| 475. |
A directional coupler is used |
| A. | to transmit microwave signals |
| B. | to generate microwave signals |
| C. | to measure amplitude and phase of a travelling wave |
| D. | both (a) and (b) |
| Answer» D. both (a) and (b) | |
| 476. |
Which of the following is not used as a microwave mixer or detector? |
| A. | PIN diode |
| B. | Crystal diode |
| C. | Schottky barrier diode |
| D. | Backward diode |
| Answer» B. Crystal diode | |
| 477. |
Consider the following statements about instrument landing system of aircraft It ensures correct landing under conditions of low visibility.It consists of runaway localizer, glide path equipment and marker beacons.It is basically a blind landing system. Which of above statements are correct? |
| A. | All |
| B. | 1 and 2 only |
| C. | 1 and 3 only |
| D. | 2 only |
| Answer» B. 1 and 2 only | |
| 478. |
To ensure that only dominant mode TE10 is allowed to propagate in an air filled rectangular waveguide, the lower frequency limit and upper frequency limit are |
| A. | about 25% above fc for TE10 and 5% below fc for TE20 mode respectively |
| B. | about 50% above fc for TE10 and 25% below fc for TE20 mode respectively |
| C. | about 25% above fc for TE10 and 25% below fc for TE20 mode respectively |
| D. | none of the above |
| Answer» B. about 50% above fc for TE10 and 25% below fc for TE20 mode respectively | |
| 479. |
In a TWT the amplitude of resultant wave travelling down the helix |
| A. | increases exponentially |
| B. | increases linearly |
| C. | decreases exponentially |
| D. | is almost constant |
| Answer» B. increases linearly | |
| 480. |
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 | |
| 481. |
The component in the given figure is |
| A. | attenuator |
| B. | T type low pass filter |
| C. | T type high pass filter |
| D. | phase shifter |
| Answer» C. T type high pass filter | |
| 482. |
If antenna diameter is increased four times, the maximum range is increased by a factor of |
| A. | 2 |
| B. | 2 |
| C. | 4 |
| D. | 0.2 |
| Answer» D. 0.2 | |
| 483. |
In a klystron amplifier dc electron velocity is v0 and dc electron charge density is r0 the dc beam current is |
| A. | r0v0 |
| B. | r0/v0 |
| C. | v0/r0 |
| D. | (v0/r0)2 |
| Answer» B. r0/v0 | |
| 484. |
To ensure that only dominant TE10 mode propagates in a rectangular waveguide, the operating frequency |
| A. | must be more than cutoff frequency of TE10 mode |
| B. | must be less than cutoff frequency of TE20 mode |
| C. | must be more than cutoff frequency of TE10 mode and less than cutoff frequency of TE20 mode |
| D. | must be less than cutoff frequency of TE10 mode |
| Answer» D. must be less than cutoff frequency of TE10 mode | |
| 485. |
Which of the following is not a travelling wave? |
| A. | e = Em sin (βx - ωt) |
| B. | e = Em cos (βx - ωt) |
| C. | e = Em sin (ωt - βx) |
| D. | e = Em sin (βx) |
| Answer» E. | |
| 486. |
A TR (transmitter receiver) tube has |
| A. | low loss for low power signals and high |
| B. | high loss for low power signals and low loss for high level signal |
| C. | low loss for both low level and high level signals |
| D. | high loss for both low level and high level signals |
| Answer» B. high loss for low power signals and low loss for high level signal | |
| 487. |
Roughly the time required for microwave cooking as compared to conventional cooking is |
| A. | about twice |
| B. | about half |
| C. | about 10 times |
| D. | about one-tenth |
| Answer» E. | |
| 488. |
The width of a radio beam from a 1 m diameter parabolic antenna at 10 GHz is about |
| A. | 100° |
| B. | 50° |
| C. | 5° |
| D. | 1° |
| Answer» D. 1¬∞ | |
| 489. |
The electrical requirement on wall thickness of rectangular wave guide is |
| A. | wall thickness is more than skin depth |
| B. | wall thickness is less than skin depth |
| C. | wall thickness is equal to skin depth |
| D. | either (b) or (c) |
| Answer» B. wall thickness is less than skin depth | |
| 490. |
Assertion (A): The impedance of a matched load is equal to characteristic impedance of line.Reason (R): A matched termination absorbs all the power incident on it. |
| 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 | |
| 491. |
In microwave detector used in laboratory measurements of relative power levels, standing wave ratio is about |
| A. | 0.1 |
| B. | 1.25 |
| C. | 5 |
| D. | 10 |
| Answer» C. 5 | |
| 492. |
Oscillations are obtained from a reflex klystron only for combinations of anode voltage and repeller voltage that give a favourable transit time. |
| A. | 1 |
| B. | |
| C. | 10 mW |
| D. | 15 mW |
| Answer» B. | |
| 493. |
The expression HZ = C cos(Bx) cos(Ay)yz is for |
| A. | TE wave |
| B. | TM waves |
| C. | both TE and TM waves |
| D. | some TE and some TM waves |
| Answer» B. TM waves | |
| 494. |
Out of modes TE20 and TE30 of propagation of electromagnetic engery |
| A. | both have the same cutoff frequency |
| B. | TE20 has lower cut off frequency as compared to TE30 |
| C. | TE30 has lower cutoff frequency as compared to TE20 |
| D. | either (a) or (c) |
| Answer» C. TE30 has lower cutoff frequency as compared to TE20 | |
| 495. |
Which of the following devices uses a helix? |
| A. | Klystron amplifier |
| B. | Klystron oscillator |
| C. | TWT |
| D. | Both (a) and (b) |
| Answer» D. Both (a) and (b) | |
| 496. |
In a travelling wave tube distributed interaction between an electron beam and a travelling wave takes place |
| A. | 1 |
| B. | |
| Answer» B. | |
| 497. |
The skin depth at 1000 MHz as compared to that at 500 MHz is |
| A. | 2 |
| B. | 12 |
| C. | 0.707 |
| D. | 0.5 |
| Answer» D. 0.5 | |
| 498. |
In rectangular waveguides the ratio of width to height is about |
| A. | 0.5 |
| B. | 1 |
| C. | 2 |
| D. | 4 |
| Answer» D. 4 | |
| 499. |
A circular waveguide has an infinite set of TE and TM modes. |
| A. | 1 |
| B. | |
| C. | Ez and Hz are both zero |
| D. | In TE mode Ez is zero and in TM mode Hz is zero |
| Answer» B. | |
| 500. |
Assertion (A): TWT uses a focussing mechanism to prevent the electron beam from spreading.Reason (R): In a TWT the electron beam has to travel a much longer distance than in klystron. |
| 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 | |