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.
| 301. |
The secondary constants of a line are |
| A. | Z0 |
| B. | Z0 and γ |
| C. | Z0, γ and wave velocity |
| D. | Z0, γ and L |
| Answer» C. Z0, Œ≥ and wave velocity | |
| 302. |
In the given figure forward current wave has a magnitude of |
| A. | 0.45 A |
| B. | 0.3 A |
| C. | 0.2 A |
| D. | 0.1 A |
| Answer» C. 0.2 A | |
| 303. |
In p mode of operation of magnetron the spikes due to phase focussing effect rotate at an angular velocity corresponding to |
| A. | one pole/cycle |
| B. | two pole/cycle |
| C. | four pole/cycle |
| D. | six pole/cycle |
| Answer» C. four pole/cycle | |
| 304. |
The radiation resistance of a doublet antenna of length dl is proportional to |
| A. | δ l |
| B. | (δ l)2 |
| C. | (δ l)3 |
| D. | (δ l)05 |
| Answer» C. (Œ¥ l)3 | |
| 305. |
Wave guides are pressurised above normal atmospheric pressure for |
| A. | increasing the power handling capacity |
| B. | improving conductivity of walls |
| C. | preventing higher modes from propagation |
| D. | varying the wave impedance |
| Answer» B. improving conductivity of walls | |
| 306. |
In high frequency circuits impedance matching can be done by open circuited stubsshort circuited stubstransformer 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 | |
| 307. |
In a microwave power measurement using bolometer, the principle of working is variation of |
| A. | inductance with absorption of power |
| B. | resistance with absorption of power |
| C. | capacitance with absorption of power |
| D. | cavity dimension with heat generated by power |
| Answer» C. capacitance with absorption of power | |
| 308. |
Fibers have numerical aperture (NA) in the range of 0.15 to 0.4 Fibers with higher NA value would have |
| A. | reduced losses |
| B. | high bandwidth |
| C. | reduced losses and low bandwidth |
| D. | more losses and low bandwidth |
| Answer» E. | |
| 309. |
Varactor diodes use |
| A. | silicon |
| B. | GaAs |
| C. | either (a) or (b) |
| D. | neither (a) nor (b) |
| Answer» D. neither (a) nor (b) | |
| 310. |
A reflex klystron oscillator uses |
| A. | one cavity resonator |
| B. | two cavity resonators |
| C. | three cavity resonators |
| D. | none of the above |
| Answer» B. two cavity resonators | |
| 311. |
A wave Em cos (bx - ωt) is a backward wave. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 312. |
In TE and TM modes of rectangular waveguides having propagation in z direction |
| A. | Ez and Hz are both zero |
| B. | In TE mode Ez is zero and in TM mode Hz is zero |
| C. | In TE mode Hz is zero and in TM mode Ez is zero |
| D. | In both TE and TM modes both Ez and Hz are non-zero |
| Answer» C. In TE mode Hz is zero and in TM mode Ez is zero | |
| 313. |
Assertion (A): Impedance matching can be done by using stubs.Reason (R): A double stub is used for impedance matching when frequency of signal varies. |
| 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 | |
| 314. |
In the given figure a short circuited transmission line resonator If n = 1, 2, 3... |
| A. | For series reasonance βl = np and for parallel resonance |
| B. | For series resonance and for parallel resonance βl = np |
| C. | βl = np for both series and parallel resonance |
| D. | for both series and parallel resonance |
| Answer» B. For series resonance and for parallel resonance Œ≤l = np | |
| 315. |
In the given figure the reflected current wave after first reflection is |
| A. | 0.18 A |
| B. | -0.18 A |
| C. | 0.3 A |
| D. | -0.3 A |
| Answer» C. 0.3 A | |
| 316. |
The duty cycle of a radar transmitter is equal to |
| A. | (PRF) (pulse width) |
| B. | (PRF)/(pulse width) |
| C. | (pulse width)/(PRF) |
| D. | (pulse width) + (PRF) |
| Answer» B. (PRF)/(pulse width) | |
| 317. |
The magnitudes of OC and SC input impedances of a transmission line an 100 Ω and 25 Ω. The characteristic impedance is |
| A. | 25 Ω |
| B. | 50 Ω |
| C. | 75 Ω |
| D. | 100 Ω |
| Answer» C. 75 Œ© | |
| 318. |
Interference generated by electrical equipment and automobile ignition systems when observed closed to earth is |
| A. | horizontally polarized |
| B. | vertically polarized |
| C. | polarized both horizontally |
| D. | not polarized |
| Answer» C. polarized both horizontally | |
| 319. |
Microwaves |
| A. | get reflected by ionosphere |
| B. | are absorbed by ionosphere |
| C. | are neither reflected nor absorbed by ionosphere |
| D. | are both reflected and absorbed by ionosphere |
| Answer» D. are both reflected and absorbed by ionosphere | |
| 320. |
In the given figure shows a 10dB directional coupler. If power input at port 1 is 100 mW, power output at port 3 is |
| A. | 10 mW |
| B. | 15 mW |
| C. | 20 mW |
| D. | 25 mW |
| Answer» B. 15 mW | |
| 321. |
In a waveguide the dielectric region is generally |
| A. | air |
| B. | magnetic material |
| C. | brass |
| D. | mica |
| Answer» B. magnetic material | |
| 322. |
PIN diode has |
| A. | p+ and n layers separated by i layer |
| B. | p+ and n+ layers separated by i layer |
| C. | p- and n- layers separated by i layer |
| D. | none of the above |
| Answer» C. p- and n- layers separated by i layer | |
| 323. |
A line of length slightly less than and short 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 | |
| 324. |
In a klystron amplifier the transit time of electron passing the gap in the cavity should be |
| A. | less than one cycle |
| B. | less than half cycle |
| C. | less than quarter cycle |
| D. | more than quarter cycle |
| Answer» D. more than quarter cycle | |
| 325. |
Consider the following statements Usable bandwidth of ridge wave guide is more than that of rectangular waveguide.For a given value of TM10 cutoff frequency the cross section of ridge wave guide is lesser that that of rect angular waveguide.Ridge wave guide has higher conductor losser than a rectangular waveguide.Ridge guide has higher conductor losser than a rectangular waveguide. Which of the above statements are correct? |
| A. | 1 and 2 only |
| B. | 1, 2 and 3 only |
| C. | 2 and 3 only |
| D. | All |
| Answer» C. 2 and 3 only | |
| 326. |
Which mode has the lowest cut off frequency in circular wave guides? |
| A. | TE01 |
| B. | TE11 |
| C. | TE20 |
| D. | TE21 |
| Answer» C. TE20 | |
| 327. |
In a backward wave oscillator the efficiency |
| A. | is much higher than in TWT |
| B. | is much lower than in TWT |
| C. | is almost the same as in TWT |
| D. | either (a) or (b) |
| Answer» D. either (a) or (b) | |
| 328. |
Ga As exhibits negative differential mobility |
| A. | 1 |
| B. | |
| Answer» B. | |
| 329. |
If f is the frequency of electromagnetic wave, fc is cutoff frequency, then in a rectangular waveguide |
| A. | attenuation is low when f > fc |
| B. | attenuation is low when f < fc |
| C. | attenuation is high when f < fc |
| D. | either (b) or (c) |
| Answer» B. attenuation is low when f < fc | |
| 330. |
A klystron amplifier generally uses Pierce gun |
| A. | 1 |
| B. | |
| Answer» B. | |
| 331. |
High speed logic circuits use |
| A. | pulses with very small width |
| B. | pulses with very large width |
| C. | pulses whose width is neither small nor large |
| D. | either (b) or (c) |
| Answer» B. pulses with very large width | |
| 332. |
For a given operating frequency a waveguide has more power handling capacity than a coaxial line. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 333. |
If a line having Z0 = 300 ∠ 0 W is short circuited at far end, VSWR is |
| A. | 0  |
| B. | 1 |
| C. | ‚àû |
| D. | 2 |
| Answer» D. 2 | |
| 334. |
In a microwave coaxial cable the inner conductor radius is a and inner radius of outside conductor is b. For TE11 mode the cut off wavelength is about |
| A. | a + b |
| B. | p(a + b) |
| C. | pa |
| D. | pb |
| Answer» C. pa | |
| 335. |
Depth of penetration does not depend on frequency. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 336. |
The directive gain of a transmitting antenna is |
| A. | proportional to wavelength |
| B. | inversely proportional to wavelength |
| C. | proportional to square of wavelength |
| D. | inversely proportional to square of wavelength |
| Answer» E. | |
| 337. |
Assertion (A): For high frequency lines inductive reactance is very high as compared to ac resistance.Reason (R): Due to skin effect ac resistance of line is higher than dc resistance. |
| 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 | |
| 338. |
The attenuation characteristics of a loaded line is similar to that of |
| A. | low pass filter |
| B. | high pass filter |
| C. | band pass filter |
| D. | band stop filter |
| Answer» E. | |
| 339. |
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 | |
| 340. |
Consider the following statements about radar Beacon It is also called transponder.It includes pulse transmitter, receiver and antenna.It replies with full power even when the signal receives is weak. Which of the above statements are correct? |
| A. | All |
| B. | 1 and 2 only |
| C. | 2 and 3 only |
| D. | 2 only |
| Answer» B. 1 and 2 only | |
| 341. |
For a 1 cm x 2 cm air filled rectangular waveguide the maximum frequency should be less than about |
| A. | 1000 MHz |
| B. | 5000 MHz |
| C. | 14000 MHz |
| D. | 140000 MHz |
| Answer» D. 140000 MHz | |
| 342. |
When a wave reaches an open circuit |
| A. | the voltage at termination is doubled the incident voltage |
| B. | the current at termination is doubled the incident voltage |
| C. | the voltage at termination is zero |
| D. | both V and I at termination are doubled the incident voltage and current |
| Answer» B. the current at termination is doubled the incident voltage | |
| 343. |
In the given figure shows the equivalent circuit of a magic tee. If all ports are matched |
| A. | nE = nH = 2 |
| B. | nE = nH = 0.707 |
| C. | nE = 2, nH = 0.707 |
| D. | nH = 0.707, nH = 2 |
| Answer» B. nE = nH = 0.707 | |
| 344. |
Which of the following statements is not correct regarding modes of electromagnetic energy transmission? |
| A. | In TE mode the direction of electric field is always and everywhere transverse to the direction of propagation |
| B. | In TM mode the magnetic field pattern is always and everywhere transverse to the direction of propagation |
| C. | The subscripts is TE and TM designations denote the number of half sine wave variations of the field components in x and y directions respectively. |
| D. | TM11 is called the dominant mode. |
| Answer» E. | |
| 345. |
A (75 - J50) ohm load is connected to a coaxial of Z0 = 75 ohm at 10 GHz. The best method of matching is to connect |
| A. | an inductance at load |
| B. | a short circuited stub at load |
| C. | a short circuited stub at specific distance from load |
| D. | a capacitance at specific distance from load |
| Answer» D. a capacitance at specific distance from load | |
| 346. |
The number of TV channels which can be accommodated in a spectrum of 300 MHz is about |
| A. | 5 |
| B. | 10 |
| C. | 50 |
| D. | 200 |
| Answer» D. 200 | |
| 347. |
Consider the following statements Dissipative attenuator has a fixed value of attenuation.Reflective attenuator has a fixed value of attenuation.Both dissipative and reflective attenuators are available only with fixed attenuation.Both dissipative and reflective attenuators are available with either fixed or variable attenuation. Which of the above are correct? |
| A. | 1 only |
| B. | 1 and 2 |
| C. | 1, 2 and 3 |
| D. | 4 only |
| Answer» E. | |
| 348. |
A rectangular waveguide has two stubs each length connected at the source end. The stubs are short circuted. Then |
| A. | the longitudinal current is power current and current in stubs is reactive |
| B. | the longitudinal current is reactive current and current in stubs is power current |
| C. | both power and reactive exists in both longitudinal direction and stubs |
| D. | the current in stubs is zero |
| Answer» B. the longitudinal current is reactive current and current in stubs is power current | |
| 349. |
Assertion (A): Bolometer is frequently used in microwave power measurement.Reason (R): In a bolometer the input microwave power causes a change in resistance. |
| 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 | |
| 350. |
A line slightly longer than length and short circuited at far end behaves as |
| A. | an inductance |
| B. | a capacitance |
| C. | L and C in series |
| D. | L and C in parallel |
| Answer» C. L and C in series | |