MCQOPTIONS
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MCQOPTIONS
This section includes 1085 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.
| 401. |
Industrial heating furnaces such as arc and induction furnaces operate on __________ power factor |
| A. | low leading |
| B. | low lagging |
| C. | high leading |
| D. | very low lagging |
| Answer» E. | |
| 402. |
For a uniform plane wave of frequency 10⁶ Hz propagating in a good conductor, the field undergoes a change in phase by 2π radius over a distance of 1 meter. The field is attenuated by a factor of 1/e at a distance of |
| A. | 1/2π m |
| B. | 1/π m |
| C. | π m |
| D. | 2π m |
| Answer» B. 1/π m | |
| 403. |
A dipole antenna of λ/8 length has an equivalent total loss resistance of 1.5 Ω. The efficiency of the antenna is |
| A. | 0.89159% |
| B. | 8.9159% |
| C. | 89.159% |
| D. | 891.59% |
| Answer» D. 891.59% | |
| 404. |
A transmission line of characteristic impedance z0 = 50 Ω. Phase Velocity = 2 x 10⁸ m/sec, and length l = 1 m is terminated by a load z1 = (30 - j 40) ohms. The input impedance of the line for a frequency of 100 MHz will be |
| A. | (30 + j x 40) Ω |
| B. | (30 - j 40) Ω |
| C. | (50 + j x 40) Ω |
| D. | (50 - j 40) Ω |
| Answer» C. (50 + j x 40) Ω | |
| 405. |
A transmission line having 50 Ω impedance is terminated in a load of (40 + j 30) Ω. The VSWR is |
| A. | j 0.033 |
| B. | 0.8.+ j 0.6 |
| C. | 1 |
| D. | 2 |
| Answer» E. | |
| 406. |
Radiation intensity of a dipole depends strongly on frequency. If at a frequency f, the intensity of radiation is 'I'. Then at a frequency of f/2, the intensity will be |
| A. | I/2 |
| B. | I/4 |
| C. | I/8 |
| D. | I/16 |
| Answer» B. I/4 | |
| 407. |
Which of the following is λ/2 length? |
| A. | Marconi |
| B. | Hertz |
| C. | Parabolic |
| D. | Yagi-uda |
| Answer» C. Parabolic | |
| 408. |
The phase angle corresponding to λ/4 in a standing-wave pattern is |
| A. | 30° |
| B. | 90° |
| C. | 135° |
| D. | 180° |
| Answer» C. 135° | |
| 409. |
The effective length of an λ/2 antenna (Given Rr = 73 Ω and (Ae)max = 0.13 λ² and η = 120 π is __________ . |
| A. | 0.6348 λ |
| B. | 0.317 λ |
| C. | 0.158 λ |
| D. | 0.371 λ |
| Answer» C. 0.158 λ | |
| 410. |
Which of the following antennas is λ /4 length? |
| A. | Dipole |
| B. | Marconi |
| C. | Monopole |
| D. | Parabolic |
| Answer» B. Marconi | |
| 411. |
Find the radiation resistance of an antenna of length λ/10 meter? |
| A. | 8 Ω |
| B. | 780 Ω |
| C. | 7.8 Ω |
| D. | 78 Ω |
| Answer» D. 78 Ω | |
| 412. |
Calculate the critical frequency for the E layer if maximum ionic densities are 3 x 10⁶ |
| A. | 15.58 x 10⁶ |
| B. | 15.58 kHz |
| C. | 1.58 x 10³ |
| D. | None of the above |
| Answer» C. 1.58 x 10³ | |
| 413. |
A transmission line has primary constants R, L, G and C and secondary constant z₀ and γ = (α + Jβ). If the line is loss less, then |
| A. | R = 0, G ≠ 0, and a = 0 |
| B. | R = 0, G = α, 0 and β = |r| |
| C. | G = 0, α = β |
| D. | R = 0, G = 0, α = 0, β = |r| |
| Answer» B. R = 0, G = α, 0 and β = |r| | |
| 414. |
Maximum effective aperture of a λ/2 antenna is |
| A. | 1.3 λ² |
| B. | 0.13 λ² |
| C. | 13 λ² |
| D. | 3.1 λ² |
| Answer» C. 13 λ² | |
| 415. |
For a rectangular waveguide (a x b, a > b) to support only the TE₁₀ mode at wavelength which one of the following pairs of in equalities is to be satisfied? |
| A. | b < λ < 2b; λ > 2a |
| B. | b < λ < 2b; λ < 2a |
| C. | a < λ < 2b; λ < 2a |
| D. | a < λ < 2b; λ > 2a |
| Answer» E. | |
| 416. |
The √(L/C) has the dimension of |
| A. | time |
| B. | capacitance |
| C. | velocity |
| D. | resistance |
| Answer» E. | |
| 417. |
The radiation resistance of a resonant long wire antenna of half wavelength (λ/2) is given |
| A. | 73 Ω |
| B. | 120 π |
| C. | 377 Ω |
| D. | 7.3 Ω |
| Answer» B. 120 π | |
| 418. |
Calculate the directivity of a given linear end fire, uniform array of 20 element, each separated by λ/3 |
| A. | 100 |
| B. | 10 |
| C. | 26.66 |
| D. | 30 |
| Answer» D. 30 | |
| 419. |
Δ²V = - ρ/E is known as __________ equation |
| A. | Poisson |
| B. | Fourier |
| C. | Laplace |
| D. | Maxwell |
| Answer» B. Fourier | |
| 420. |
Capacitance hats are installed on low frequency antenna is |
| A. | increase the electrical length |
| B. | reduce the electrical length |
| C. | protect against lightening |
| D. | protect against corona effects |
| Answer» B. reduce the electrical length | |
| 421. |
The value of VSWR is taken as ∞ when the line is |
| A. | short-circuited |
| B. | open-circuited |
| C. | terminated with full load |
| D. | terminated with load equal to the characteristic impedance of the load |
| Answer» C. terminated with full load | |
| 422. |
An electric charge Q is placed in a dielectric medium which of the following quantities are independent of the dielectric constant ε of the medium |
| A. | electric potential V and electric field intensity E |
| B. | displacement density D and displacement φ |
| C. | electric field intensity E and displacement φ |
| D. | electric potential V and displacement φ |
| Answer» C. electric field intensity E and displacement φ | |
| 423. |
In a 100 turn coil, if the flux through each turn is (t³ - 2t)mWb, the magnitude of the induced emf in the coil at a time of 4 sec is |
| A. | 46 mV |
| B. | 56 mV |
| C. | 4.6 V |
| D. | 5.6 V |
| Answer» D. 5.6 V | |
| 424. |
An antenna has 40 Ω resistance and 60 Ω radiation resistance. The efficiency of the antenna is |
| A. | 30% |
| B. | 40% |
| C. | 50% |
| D. | 60% |
| Answer» E. | |
| 425. |
When a plane wave travelling in free space is incident normally on a medium having εr = 4.0, then fraction of power transmitted into the medium is given by |
| A. | 8/9 |
| B. | 1/2 |
| C. | 1/3 |
| D. | 5/6 |
| Answer» B. 1/2 | |
| 426. |
Consider an arbitrary distribution of conducting bodies in a charge free space according to the uniqueness theorem, which of following are required to be specified in order that the field is uniquely determined everywhere? 1. Total charge on each conductor2. Potential at each conductor surface3. Potential at same of conductor and total charge on the remainder4. Total charge as well as potential gradient on each conductor surface Select the correct answer using the codes given below codes |
| A. | 1 and 3 |
| B. | 2 and 4 |
| C. | 1, 2, and 3 |
| D. | 1, 2, 3, 4 |
| Answer» C. 1, 2, and 3 | |
| 427. |
∇² is |
| A. | vector |
| B. | scalar |
| C. | depend on direction |
| D. | none |
| Answer» C. depend on direction | |
| 428. |
A field given below can be |
| A. | harmonic |
| B. | divergence less |
| C. | solenoidal |
| D. | rotational |
| Answer» E. | |
| 429. |
Laplace equation in cylindrical co-ordinates is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 430. |
For an incident wave which is normal on the perfect dielectric the reflection factor is given by (where ε1 and ε2 are the permittivities of 1st and 2nd medium respectively) |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» E. | |
| 431. |
The characteristic equation of plane wave in E independent of two dimensions y and z is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 432. |
Which one of the following is correct expression. Where t is torque, B magnetic field, M is the moment |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 433. |
Antenna aperture efficiency is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 434. |
Divergence theorem relate surface integration with volume integration as |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 435. |
The radiation pattern of helical antenna (axial mode) is represented by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 436. |
Given the following equation, if the radiation intensity of an antenna is proportional to sin² θ, where θ is the elevation angle, the antenna directivity will be |
| A. | 8/3π |
| B. | 16/3π |
| C. | 4π/3 |
| D. | 3π/8 |
| Answer» E. | |
| 437. |
Which of the following statement is incorrect? |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» E. | |
| 438. |
Which one set of the following Maxwell's equation gives the basic idea of radiation ? |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 439. |
A TEM wave incident obliquely on a dielectric boundary with εr1 = 2 and εr2 = 1, the angle of incidence for total reflection is |
| A. | 30° |
| B. | 60° |
| C. | 45° |
| D. | 90° |
| Answer» D. 90° | |
| 440. |
An antenna having an effective temperature of 27°K is fed into a microwave amplifier that has an effective noise temperature of 30 K. Calculate the available noise power per unit bandwidth |
| A. | 30 K |
| B. | 57 K |
| C. | 27 K |
| D. | 3K, K is Boltzmann constant |
| Answer» C. 27 K | |
| 441. |
A plane EM wave is travelling in an unbound loss less dielectric having μy = 1 and εy = 4, the time average Poynting vector of the wave is 5 W/m³ . The phase velocity vp (assuming velocity of light as 3 x 10⁸ m/sec) is |
| A. | 1.5 x 10⁸ m/sec |
| B. | 3 x 10⁸ m/sec |
| C. | 2.5 x 10⁸ m/sec |
| D. | 0.5 x 10⁸ m/sec |
| Answer» B. 3 x 10⁸ m/sec | |
| 442. |
When a plane wave is incident normally from dielectric '1' (μ₀, ε1) onto dielectric '2' (μ₀, ε2) the electric field of the transmitted wave is 2 times the electric field of the reflected wave. The ratio ε2/ε1 is |
| A. | 0.5 |
| B. | 1 |
| C. | 2 |
| D. | 4 |
| Answer» E. | |
| 443. |
Radiation resistance of half-wave dipole (λ/2) antenna is in free space |
| A. | 73 Ω |
| B. | 120 π |
| C. | 36.5 Ω |
| D. | 70 Ω |
| Answer» B. 120 π | |
| 444. |
The refractive index of E layer, if angle of incidence is 30° |
| A. | 0.5 |
| B. | 0.25 |
| C. | 0 |
| D. | 1 |
| Answer» B. 0.25 | |
| 445. |
The displacement flux density at a point on the surface of a perfect conductor is D = 2(ax - √3 az)c/m² pointing away from the surface. The charge density at that point c/m² will be |
| A. | 2 |
| B. | - 2 |
| C. | 4 |
| D. | - 4 |
| Answer» D. - 4 | |
| 446. |
The directive gain of λ/2 resonant wire is 1.64. |
| A. | True |
| B. | False |
| C. | May be True or False |
| D. | Can't say |
| Answer» B. False | |
| 447. |
A (75 - j 40) W load is connected to a co-axial line of z0 = 75ω at 6 MHz. The load matching on the line can be accomplished by connecting |
| A. | a short circuit stub at the load |
| B. | an inductance at the load |
| C. | a short circuit stub at a specific distance from the load |
| D. | a capacitance at a specific distance from the load |
| Answer» C. a short circuit stub at a specific distance from the load | |
| 448. |
The Q of a resonant transmission line is |
| A. | Q = L/R |
| B. | Q = WL/R |
| C. | Q = L/WR |
| D. | Q = W/LR |
| Answer» C. Q = L/WR | |
| 449. |
The unit of ∇ x H is |
| A. | Ampere |
| B. | Ampere/meter |
| C. | Ampere/m² |
| D. | Ampere-meter |
| Answer» D. Ampere-meter | |
| 450. |
A λ/8 section of transmission line is determined of load impedance of (2 - j 5) Ω. If characteristic impedance of line is 10 Ω. Then input impedance of line is |
| A. | 10 Ω |
| B. | (6.9 + j 7.24) Ω |
| C. | (1.75 + j 3.098) Ω |
| D. | (2 - j 5) Ω |
| Answer» D. (2 - j 5) Ω | |