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.
| 451. |
It is desired to reduce the reflection at an air porcelain by use of 7/4 plate (for Porcelain μ = 40, and εr = 7). The thickness of the polystyrene plate required at 10 GHz will be |
| A. | 5.039 cm |
| B. | 50.39 cm |
| C. | 0.5039 cm |
| D. | 0.05039 cm |
| Answer» D. 0.05039 cm | |
| 452. |
The voltage and current distributions on a grounded λ/4 dipole (Marconi antenna) are similar to those of a half wave dipole in space. |
| A. | True |
| B. | False |
| C. | May be True or False |
| D. | Can't say |
| Answer» B. False | |
| 453. |
The equation ∇ . J = 0 is called |
| A. | Poisson's equation |
| B. | Kirchoff's node equation |
| C. | Continuity equation for static currents |
| D. | Continuity equation for sampling currents |
| Answer» D. Continuity equation for sampling currents | |
| 454. |
If ωε is the displacement current factor and s is conduction current density factor then which of the following statements is incorrect? |
| A. | For a lossless dielectric σ = 0 |
| B. | For an imperfect dielectric σ = 0 |
| C. | For a dielectric ωε >> σ |
| D. | For a semiconductor ωε = σ |
| Answer» C. For a dielectric ωε >> σ | |
| 455. |
A material has conductivity of 10¯² mho/m and a relative permittivity of 4. The frequency at which conduction current in the medium is equal to displacement current is |
| A. | 45 MHz |
| B. | 90 MHz |
| C. | 450 MHz |
| D. | 900 MHz |
| Answer» B. 90 MHz | |
| 456. |
Antenna efficiency of antenna is, if radiation resistance is 370 Ω and loss resistance is 100 Ω |
| A. | 80% |
| B. | 87% |
| C. | 78% |
| D. | 21.27% |
| Answer» D. 21.27% | |
| 457. |
Distilled water at 25°C is characterized by σ = 1.7 x 10¯⁴ mho/m and ε = 78 ε₀ at a frequency of 3 GHz. Its loss tangent is (ε = 10¯⁹/36π F/m) |
| A. | 1.3 x 10¯⁵ |
| B. | 1.3 x 10¯³ |
| C. | 1.7 x 10¯⁴/78 |
| D. | 1.7 x 10¯⁴/78ε₀ |
| Answer» B. 1.3 x 10¯³ | |
| 458. |
Induction and radiation fields are equal at a distance equal to |
| A. | 6/λ |
| B. | 6λ |
| C. | λ/6 |
| D. | λ/2π |
| Answer» E. | |
| 459. |
In a uniform linear array, four isotropic radiating elements are spaced λ/4 apart. The progressive phase shift between the elements required for forming the main beam at 60° off the end fire is |
| A. | -π radius |
| B. | -π/2 radius |
| C. | -π/4 radius |
| D. | -π/8 radius |
| Answer» D. -π/8 radius | |
| 460. |
A 50 π characteristic impedance line is connected to a load which shows a reflection coefficients of 0.268. If Vin = 15 volt, then the net power delivered to the load will be |
| A. | 0.139 W |
| B. | 1.39 W |
| C. | 0.278 W |
| D. | 2.78 W |
| Answer» C. 0.278 W | |
| 461. |
Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of 10¹⁴ Hz in glass. Assume velocity of light is 3 x 10⁸ m/sec in vacuum. |
| A. | 4 μm |
| B. | 3 μm |
| C. | 2 μm |
| D. | 1 μm |
| Answer» D. 1 μm | |
| 462. |
The induction field of short current element varies as |
| A. | 1/r |
| B. | 1/√r |
| C. | 1/r² |
| D. | 1/r³ |
| Answer» E. | |
| 463. |
A rectangular waveguide (2.29 x 1.02) cm operates at a freq. of 11 GHz in TE₁₀ mode. If the maximum potential gradient of the signal is 5 kV/cm, then the maximum power handling capacity of the waveguide will be |
| A. | 31.11 mW |
| B. | 31.11 W |
| C. | 31.11 kW |
| D. | 31.11 MW |
| Answer» D. 31.11 MW | |
| 464. |
The I/P impedance of a λ/8 long short circuited section of a loss less transmission line is |
| A. | zero |
| B. | inductive |
| C. | capacitance |
| D. | infinite |
| Answer» C. capacitance | |
| 465. |
The input impedance of short-circuited line of length l where λ/4 < l < λ/2, is |
| A. | resistive |
| B. | inductive |
| C. | capacitive |
| D. | none of the above |
| Answer» D. none of the above | |
| 466. |
For transmission of waveform a dielectric medium of permittivity ε1 into a dielectric medium of lower permittivity ε2 , (ε1 > ε2) the critical angle of incidence θc (relative to the interface) is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 467. |
An isolated sphere in air has a radius equal to 1/4πε₀ meter, its capacitance is |
| A. | πF |
| B. | 1F |
| C. | 4πF |
| D. | 1/4πF |
| Answer» C. 4πF | |
| 468. |
ZL = 200 Ω and it is desired that Zi = 50 Ω The quarter wave transformer should have a characteristic impedance of |
| A. | 100 Ω |
| B. | 40 Ω |
| C. | 10000 Ω |
| D. | 4 Ω |
| Answer» B. 40 Ω | |
| 469. |
If a plane electromagnetic wave satisfies the equation given below, the wave propagates in the (at an angle of 45° between the x and z direction) |
| A. | x-direction |
| B. | z-direction |
| C. | y direction |
| D. | xy plane |
| Answer» C. y direction | |
| 470. |
Medium 1 has the electrical permittivity ε1 = 1.5 ε0 farad/m and occupies the region to the left of x = 0 plane. Medium 2 has the electrical permittivity ε2 = 2.5 ε0 farad/m and the occupies the region to the right of x = 0 plane. If E1 in medium 1 is given by below equation, then E2 in medium 2 is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 471. |
The sinusoidally time varying vector field is |
| A. | elliptically polarized |
| B. | circularly polarized |
| C. | linearly polarized |
| D. | unpolarized |
| Answer» E. | |
| 472. |
Find the flux crossing the plane surface defined by 0.5 ≤ r ≤ 3.5 m and 0 ≤ z ≤ 3 m. if |
| A. | 0 |
| B. | 255 Wb |
| C. | 6.45 Wb |
| D. | none of the above |
| Answer» B. 255 Wb | |
| 473. |
The directive gain of an antenna is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 474. |
The torque (in mm) acting on a circular current loop of radius 1 mm in the xy plane, connected at the origin and with current 0.1 A, flowing in the sense of increasing in a following magnetic field is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 475. |
Voltage standing wave pattern in a loss less transmission line with characteristic impedance 50 Ω and a resistive load is shown in the figure. The value of load resistance is |
| A. | 50 Ω |
| B. | 200 Ω |
| C. | 12.5 Ω |
| D. | 0 Ω |
| Answer» C. 12.5 Ω | |
| 476. |
The electric field of the incident wave is given by following equation. Where ω = 3 x 10⁹π and β = 10 π. The electric field of the transmitted wave Et is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 477. |
Two identical antennas are placed in the θ = π/2 plane as shown in the figure. The elements have equal amplitude excitation with 180° polarity difference, operating of the far-zone resultant electric field strength normalized with that of a single element, both computed for φ = 0, is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» E. | |
| 478. |
Two co-axial cylindrical sheets of charge are present in free space fs = 5 c/m² at r = 2 m and ρs = -2 c/m² at r = 4 m, The displacement flux density D at r = 3 m is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 479. |
Given figure shows a 90° sector of spherical reflector with vertex 'V', centre of curvature 'C' and equal distances VD, DF, FE and EC. When a beam of EM wave is incident parallel to the axis, all the energy will pass through the region |
| A. | VD |
| B. | DF |
| C. | EF |
| D. | EC |
| Answer» E. | |
| 480. |
Voltage standing wave pattern in a loss less transmission line with characteristic impedance 50 Ω and a resistive load is shown in the figure. Reflection coefficient is given by |
| A. | -0.6 |
| B. | -1 |
| C. | 0.6 |
| D. | 0 |
| Answer» D. 0 | |
| 481. |
If the electric field intensity is given by following equation, the potential difference between x(2, 0, 0) and y(1, 2, 3) is |
| A. | +1 volt |
| B. | -1 volt |
| C. | +5 volt |
| D. | +6 volt |
| Answer» D. +6 volt | |
| 482. |
Two identical and parallel dipole antenna are kept apart by a distance of λ/4 in the H-plane. They are fed with equal currents but the right most antenna has a phase shift of + 90°. The radiation pattern is given as |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 483. |
For a transmission line with homogeneous dielectric the capacitance per unit length is 'c', the relative permittivity of the dielectric is 'εr' and velocity of light in free space is 'v' the characteristic impedance z0 is equal to |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 484. |
Which one of the following statement is not a correct for a plane wave with |
| A. | The wave frequency is 10¯⁶ r.p.s. |
| B. | The wavelength is 3.14 m |
| C. | The wave travels + x direction |
| D. | Wave is polarized in the z direction |
| Answer» E. | |
| 485. |
What does the following expression represent? |
| A. | Electric Energy density |
| B. | Magnetic Energy density |
| C. | Power density |
| D. | Radiation Resistance |
| Answer» C. Power density | |
| 486. |
The electric field of an EM wave propagating in the z direction given by following equation. The wave is |
| A. | linearly polarized in z direction |
| B. | elliptically polarized |
| C. | left hand circularly polarized |
| D. | right hand circularly polarized |
| Answer» D. right hand circularly polarized | |
| 487. |
The radiation pattern of two element collinear array is represent in |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 488. |
A lossless transmission line is connected to two identical voltage source as shown in figure. The impedance measured at the midpoint AA' is |
| A. | ∞ |
| B. | 100 |
| C. | 50 |
| D. | 25 |
| Answer» B. 100 | |
| 489. |
In case of concentric conductors of radius a and b the value of capacitance (C) is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 490. |
The phase velocity in a transmission line is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» E. | |
| 491. |
The characteristic impedance is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 492. |
The length of a λ/2 antenna in feet is given by the relation |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 493. |
The energy stored in an electric field is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 494. |
The attenuation constant in case of a transmission line is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 495. |
The energy stored in a magnetic field is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 496. |
The attenuation factor α and phase shift factor β for a wave propagated in a good dielectric having σ/ωε >> 1 are given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 497. |
For radiation field of an antenna at a distance r varies as |
| A. | 1/r |
| B. | 1/r² |
| C. | 1/r³ |
| D. | 1/r⁴ |
| Answer» B. 1/r² | |
| 498. |
Two LOS antennas having power gains of G1 and G2 are separated transmitted power, Pr is received power turn Pr/Pt will be proportional to |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 499. |
The force acting on a charge q moving with velocity v̅ in a region of electric field E̅ and magnetic field B̅ is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 500. |
Which one of the following is not a correct Maxwell equation? |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |