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.
| 351. |
An electromagnetic wave can be completely guided by a dielectric rod or slab. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 352. |
As compared to dimensions of most feeds, the skin depth at microwave frequencies is |
| A. | of the same magnitude |
| B. | much larger |
| C. | much smaller |
| D. | either (b) or (c) |
| Answer» B. much larger | |
| 353. |
Which of the following lines behaves as infinite line? |
| A. | a line terminated in inductance |
| B. | a line terminated in capacitance |
| C. | a short line |
| D. | a line terminated in z0 |
| Answer» E. | |
| 354. |
The primary constants of a transmission line are |
| A. | R and L |
| B. | R, L and C |
| C. | R and C |
| D. | R, L, G and C |
| Answer» E. | |
| 355. |
In the given figure forward voltage wave has a magnitude |
| A. | 90 V |
| B. | 60 V |
| C. | 30 V |
| D. | 10 V |
| Answer» D. 10 V | |
| 356. |
If the minimum range of a radar is to be doubled, the peak power has to be increased by a factor of |
| A. | 2 |
| B. | 4 |
| C. | 8 |
| D. | 16 |
| Answer» E. | |
| 357. |
For matching over a range of frequencies in a transmission line it is best to use |
| A. | a balun |
| B. | a broad band directional coupler |
| C. | double stub |
| D. | a single stub of adjustable position |
| Answer» D. a single stub of adjustable position | |
| 358. |
A microwave junction is matched at all ports if the S matrix |
| A. | has all diagonal elements zero |
| B. | has all diagonal elements equal but not zero |
| C. | has all diagonal elements complex |
| D. | is Hermitian |
| Answer» B. has all diagonal elements equal but not zero | |
| 359. |
Consider the following statements about a magic tee The collinear arms are isolated from each other.On of the collinear arms is isolated from E arm.On of the collinear arms is isolated from H arm.E and H arms are isolated from each other. Of the above statements |
| A. | 1 and 2 are correct |
| B. | 1 and 3 are correct |
| C. | 1 and 4 are correct |
| D. | 2 and 3 are correct |
| Answer» D. 2 and 3 are correct | |
| 360. |
In a klystron amplifier the bunching effect |
| A. | converts velocity modulation into current modulation of beam |
| B. | converts current modulation into velocity modulation of beam |
| C. | both (c) and (b) |
| D. | neither (a) nor (b) |
| Answer» B. converts current modulation into velocity modulation of beam | |
| 361. |
A loss less line is terminated in a circular lines are E lines |
| A. | SWR = 0 |
| B. | SWE = 0 |
| C. | SWR is finite |
| D. | SWR = ‚àû |
| Answer» D. SWR = ‚àû | |
| 362. |
Characteristic impedance of a coaxial cable is inversely proportional to ‚ààr. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 363. |
For air filled circular waveguides |
| A. | the attenuation due to imperfect conducting walls is negligible |
| B. | the attenuation due to imperfect dielectric is negligible |
| C. | both the attenuation i.e. due to imperfect conducting walls and due to imperfect dielectric are significant |
| D. | the total attenuation is almost zero |
| Answer» C. both the attenuation i.e. due to imperfect conducting walls and due to imperfect dielectric are significant | |
| 364. |
The external magnetic field in a magnetron is such that lines are |
| A. | parallel to the axis of cathode |
| B. | perpendicular to the axis of cathode |
| C. | inclined to the axis of cathode |
| D. | either (b) or (c) |
| Answer» B. perpendicular to the axis of cathode | |
| 365. |
Assertion (A): A line of length slightly more than and open circuited at far end is equivalent to an inductive reactance.Reason (R): A line of length slightly more than 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 | |
| 366. |
In the given figure the reflected voltage wave after first reflection is |
| A. | 18 V |
| B. | -18 V |
| C. | 30 V |
| D. | -30 V |
| Answer» C. 30 V | |
| 367. |
If air pressure in a rectangular waveguide is increased the maximum power handling capacity |
| A. | is decreased |
| B. | is increased |
| C. | remains the same |
| D. | may increase or decrease depending on pressure |
| Answer» C. remains the same | |
| 368. |
A TE10 rectangular waveguide is to be designed for operation over 25-35 GHz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is |
| A. | 15 mm |
| B. | 10 mm |
| C. | 9 mm |
| D. | 7.5 mm |
| Answer» E. | |
| 369. |
A 'rat race' is a |
| A. | hybrid junction for microwaves |
| B. | a microwave oscillator |
| C. | a microwave amplifier |
| D. | a microwave antenna |
| Answer» B. a microwave oscillator | |
| 370. |
In a cable with ‚ààr = 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 | |
| 371. |
The correct sequence of parts in klystron amplifier are |
| A. | anode, catcher cavity, cathode, buncher cavity |
| B. | cathode, buncher cavity, catcher cavity, cavity |
| C. | anode, buncher cavity, catcher cavity, cathode |
| D. | cathode, catcher cavity, anode, buncher cavity |
| Answer» C. anode, buncher cavity, catcher cavity, cathode | |
| 372. |
If a and b are the width and height of rectangular wave-guide the cut off wavelength λc for TE20 mode is equal to |
| A. | a |
| B. | a + b |
| C. | a - b |
| D. | a2 + b2 |
| Answer» B. a + b | |
| 373. |
Fields are said to be circularly polarized if |
| A. | their magnitudes are equal |
| B. | their magnitudes are equal and they differ in phase by ± 90° |
| C. | their magnitudes are unequal and they differ in phase ± 90° |
| D. | their magnitudes are unequal and they are in phase |
| Answer» C. their magnitudes are unequal and they differ in phase ¬± 90¬∞ | |
| 374. |
As wavelength decrease the size of high directivity antenna |
| A. | decreases |
| B. | increases |
| C. | is not affected |
| D. | either (b) or (c) |
| Answer» B. increases | |
| 375. |
The resistance values of a PIN diode under positive bias and negative bias respectively are about |
| A. | a few ohms and a kilo ohms |
| B. | about 100 ohms and 1000 ohms |
| C. | about 0.1 ohm and 100 ohms |
| D. | about 1000 ohms and 10000 ohms |
| Answer» B. about 100 ohms and 1000 ohms | |
| 376. |
A line of length less than 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 | |
| 377. |
Consider the following statements Bunching of electrons occurs in two cavity klystron amplifier.Bunching of electrons occurs in multi cavity klystron amplifier.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 | |
| 378. |
A magic tee is to be used as CW duplexer. Then port 1, port 2, port 3 (E arm), port 4 (H arm) respectively should be connected to |
| A. | matched load, antenna, receiver and CW transmitter |
| B. | CW transmitter, antenna, receiver and matched load |
| C. | CW transmitter, receiver, antenna and matched load |
| D. | CW transmitter, matched load, receiver and antenna |
| Answer» B. CW transmitter, antenna, receiver and matched load | |
| 379. |
In a backward wave oscillator the wave |
| A. | travelling along the line winds itself back and forth |
| B. | progresses only in forward direction |
| C. | progresses only in backward direction |
| D. | either (a) or (c) |
| Answer» B. progresses only in forward direction | |
| 380. |
Radar reciever has high sensitivity and low noise figure |
| A. | 1 |
| B. | |
| Answer» B. | |
| 381. |
The width of a radio beam from a 1 m diameter parabolic antenna at 1 GHz is about |
| A. | 100° |
| B. | 50° |
| C. | 5° |
| D. | 2° |
| Answer» C. 5¬∞ | |
| 382. |
Which of the following modes in circular waveguides are circularly symmetric? |
| A. | TE01 |
| B. | TE02 |
| C. | both (a) and (b) |
| D. | neither (a) nor (b) |
| Answer» D. neither (a) nor (b) | |
| 383. |
In TE10 mode of rectangular waveguide |
| A. | there is one half sine wave variation along x direction and one along y direction |
| B. | there is one half sine wave variation along y direction and one along x direction |
| C. | there is one full sine wave variation along x direction and one along y direction |
| D. | none of the above |
| Answer» B. there is one half sine wave variation along y direction and one along x direction | |
| 384. |
Assertion (A): Microstrip is very commonly used in microwave integrated circuits.Reason (R): Microstrip has an easy access to the top-surface so that active and passive discrete components can be easily mounted. |
| 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 | |
| 385. |
Performance of a PIN diode switch is represented by |
| A. | insertion loss when switch is off |
| B. | insertion loss when switch is on |
| C. | insertion loss when switch is on and isolation loss when switch is off |
| D. | insertion loss when switch is off and isolation loss when switch is on |
| Answer» D. insertion loss when switch is off and isolation loss when switch is on | |
| 386. |
Reflection from the object to be measured is significant only when the wavelength is |
| A. | much bigger than the size of object |
| B. | much smaller than the size of object |
| C. | almost of the size of object |
| D. | either (a) or (c) |
| Answer» C. almost of the size of object | |
| 387. |
Hollow waveguides are used as transmission lines at frequencies |
| A. | above 1 GHz |
| B. | above 5 GHz |
| C. | above 10 MHz |
| D. | above 1 MHz |
| Answer» C. above 10 MHz | |
| 388. |
The speed at which axial electric field due to signal advances in a TWT is equal to |
| A. | speed of light |
| B. | (speed of light) (helix pitch helix circumference) |
| C. | (speed of light) (helix circumference helix pitch) |
| D. | (speed of light) (helix pitch) (helix circumference) |
| Answer» C. (speed of light) (helix circumference helix pitch) | |
| 389. |
In a line with finite attenuation |
| A. | power transmission is least efficient when there are no standing waves on the line |
| B. | power transmission is most efficient when there are no standing waves on line |
| C. | Load power depends on phase constant |
| D. | standing waves will always exist on the line |
| Answer» C. Load power depends on phase constant | |
| 390. |
The directive gain of a transmitting antenna is proportional to |
| A. | its cross-sectional area |
| B. | square of cross-sectional area |
| C. | square root of cross-sectional area |
| D. | cube root of cross-sectional area |
| Answer» B. square of cross-sectional area | |
| 391. |
Assertion (A): A half wavelength line can be used as a 1 : 1 transformer.Reason (R): The input impedance of a half wavelength line is equal to load impedance. |
| 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 | |
| 392. |
In which mode of circular waveguide does the attenuation continuously decrease as frequency is increased? |
| A. | TE01 |
| B. | TE11 |
| C. | TE05 |
| D. | TE21 |
| Answer» B. TE11 | |
| 393. |
In a shield helix |
| A. | the spacing between adjacent turns is very large |
| B. | the spacing between adjacent turns approaches zero |
| C. | the spacing between adjacent turns approaches zero and wire thickness approaches zero |
| D. | the spacing between adjacent turns is very large wire thickness approaches zero |
| Answer» D. the spacing between adjacent turns is very large wire thickness approaches zero | |
| 394. |
Loading of a line means |
| A. | increasing inductance of line |
| B. | increasing distributed inductance of line |
| C. | decreasing distributed inductance of line |
| D. | decreasing inductance of line |
| Answer» C. decreasing distributed inductance of line | |
| 395. |
In the given figure the line voltage after a number of reflections will be |
| A. | 30 V |
| B. | -30 V |
| C. | 10 V |
| D. | -10 V |
| Answer» D. -10 V | |
| 396. |
As compared to LED, LASER has higher emission efficiencyno tuning arrangementnarrow spectral widthprovision 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. | |
| 397. |
The frequency of oscillations obtained from a reflex klystron depends mainly on |
| A. | resonant frequency of cavity |
| B. | repeller voltage |
| C. | voltage of focussing electrode |
| D. | characteristics of cathode |
| Answer» B. repeller voltage | |
| 398. |
The beam of a radar should be |
| A. | very narrow |
| B. | very wide |
| C. | neither too narrow nor very wide |
| D. | either (b) or (c) |
| Answer» B. very wide | |
| 399. |
Which of the following is wrong for a magic used to tee? |
| A. | E and H arms are decoupled |
| B. | coplanar arms are coupled |
| C. | all ports are perfectly matched |
| D. | A signal into coplanar arm splits equally between E and H arms |
| Answer» C. all ports are perfectly matched | |
| 400. |
If VSWR is infinite, the transmission line is terminated in |
| A. | short circuit |
| B. | complex impedance |
| C. | open circuit |
| D. | either (a) or (c) |
| Answer» E. | |