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.
| 501. |
What is the characteristic impedance Z0 of a line having R, inductance L, capacitance C and conductance G? |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 502. |
A plane wave is characterized by following equation. The wave is |
| A. | linearly polarized |
| B. | circularly polarized |
| C. | elliptically polarized |
| D. | unpolarized |
| Answer» D. unpolarized | |
| 503. |
Most antenna consisting of a 50 meter long vertical conductor operates over a perfectly conducting ground plane. It is base fed at a frequency of 600 kHz. The radiation resistance of the antenna in ohms is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 504. |
Consider a 300 Ω, quarter wave long at 1 GHz transmission line as shown in figure. It is connected to a 10 V, 50 Ω source at one end is left open circuited at the other end. The magnitude of the voltage at the open circuit end of the line is |
| A. | 10 V |
| B. | 5 V |
| C. | 60 V |
| D. | 60/7 volt |
| Answer» B. 5 V | |
| 505. |
Which one of the following does represents the electric field lines for the TE02 mode in the cross section of a hollow rectangular metallic waveguide? |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 506. |
The critical frequency of ‘F’ layer is greater than 30 MHz. |
| A. | True |
| B. | False |
| Answer» C. | |
| 507. |
An open wire transmission line having a characteristic impedance of 600 ohms is terminated by a resistive load of 900 O. The standing wave ratio will be |
| A. | 1.5 |
| B. | 2.5 |
| C. | 3.5 |
| D. | 4.5 |
| Answer» B. 2.5 | |
| 508. |
When a conductor moves in the field, so that it makes an angle 8 with the lines of flux, the force F is given as : F = Bl sin2 0. |
| A. | Yes |
| B. | No |
| Answer» C. | |
| 509. |
Which of the following antennas is λ /4 length? |
| A. | Monopole |
| B. | Parabolic |
| Answer» B. Parabolic | |
| 510. |
According to Siegel and Labus, antenna can be treated as |
| A. | closed transmission line |
| B. | shorted transmission line |
| C. | earthed transmission line |
| D. | opened-out transmission line |
| Answer» E. | |
| 511. |
Absolute permeability (μ) is given by __________ henry/metre |
| A. | 4p x 10-12 |
| B. | 4p x 10-7 |
| C. | 8.854 x 10-12 |
| D. | 8.854 x 10-7 |
| Answer» C. 8.854 x 10-12 | |
| 512. |
Magnetic susceptibility of a medium is the ratio of |
| A. | magnetic field strength to mmf |
| B. | intensity of magnetization to magnetic flux density |
| C. | intensity of magnetization to field strength |
| D. | mmf to magnetic field strength |
| Answer» D. mmf to magnetic field strength | |
| 513. |
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 | |
| 514. |
In waveguide Degenerate modes are |
| A. | two mode having same cut off frequency |
| B. | two mode having same power |
| C. | two mode having same phase velocity |
| D. | it is a hypothetical mode |
| Answer» B. two mode having same power | |
| 515. |
A circular waveguide carries TE11 mode whose radial electric-field is given by Er = E 0J1 (r) sin φ V/m where 'r' is the radial distance in cm, from the waveguide axis. The cut-off wavelength of the mode is |
| A. | 10 cm |
| B. | 3p cm |
| C. | 2p cm |
| D. | 8 cm |
| Answer» D. 8 cm | |
| 516. |
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 | |
| 517. |
The potential that appears at a point in space due to the current which caused it is called potential |
| A. | accelerating |
| B. | retardation |
| C. | oscillating |
| D. | lagging the current |
| Answer» C. oscillating | |
| 518. |
MUF is highest in periods of greatest sunspot activity. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 519. |
For transmission-line matching over range of frequencies, it is best to use a |
| A. | single stub of adjustable position |
| B. | double stub |
| C. | broadband directional coupler |
| D. | balun |
| Answer» C. broadband directional coupler | |
| 520. |
A time varying field is applied to a circuit with a capacitor- which of the following statements is correct? |
| A. | The current in the circuit consists of conduction current and displacement current |
| B. | The displacement current passes through the capacitor |
| Answer» C. | |
| 521. |
The fluctuation in the received signal strength at the receiver of a random variation in the received signal is known as |
| A. | fluctuation |
| B. | fading |
| C. | absorption |
| D. | cycling |
| Answer» C. absorption | |
| 522. |
Coaxial cables can be used for which frequency? |
| A. | 15 kHz |
| B. | 10 MHz |
| C. | 200 MHz |
| D. | 2000 MHz |
| Answer» D. 2000 MHz | |
| 523. |
The velocity of electromagnetic wave in free space is given by |
| A. | μ0/ε0 |
| B. | μ0 . ε0 |
| C. | |
| Answer» D. | |
| 524. |
A dipole antenna of λ/8 length has an equivalent total loss resistance of 1.5 Ω. The efficiency of the antenna is |
| A. | 0.0089 |
| B. | 0.0892 |
| C. | 0.8916 |
| D. | 8.9159 |
| Answer» D. 8.9159 | |
| 525. |
The boundary conditions at the interface between two dielectrics in an electric field are given by |
| A. | Dnormal = 0, Etangential = 0 |
| B. | Dnormal = 0, Enormal = 0 |
| C. | Dtangential = 0, Etangential = 0 |
| D. | Dtangential = 0, Enormal = 0 |
| Answer» B. Dnormal = 0, Enormal = 0 | |
| 526. |
The gain of collinear arrays is maximum when the spacing between the elements is |
| A. | 0.1 λ to 0.3 λ |
| B. | 0.3 λ to 0.9 λ |
| C. | 0.5 λ to 0.7 λ |
| D. | 0.7 λ to 0.9 λ |
| Answer» C. 0.5 Œª to 0.7 Œª | |
| 527. |
If reflection coefficient is 1/5, then corresponding VSWR is given by |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 43499 |
| Answer» E. | |
| 528. |
Which of the following term does not apply to the Yagi-Uda array? |
| A. | High gain |
| B. | Folded dipole |
| C. | Parasitic |
| D. | Good bandwidth |
| Answer» B. Folded dipole | |
| 529. |
The current distribution of a half wave dipole is |
| A. | uniform |
| B. | sinusoidal |
| C. | triangular |
| D. | complex |
| Answer» C. triangular | |
| 530. |
When a magnetic circuit is compared with an electric circuit, the equivalent of the magnetic flux is |
| A. | the conductivity of the lines |
| B. | the voltage of the source |
| C. | the current in the lines |
| D. | the conductance of the load |
| Answer» D. the conductance of the load | |
| 531. |
The complex Poynting vector for electromagnetic wave. |
| A. | Im(E x Hx) |
| B. | Re(E x Hx) |
| C. | (E x H) |
| D. | E x H |
| Answer» C. (E x H) | |
| 532. |
The direction in a Yagi Uda antenna is longer than the radiating element. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 533. |
For a plane good conductor, skin depth varies |
| A. | directly as square root of permeability |
| B. | directly as square root of frequency |
| C. | inversely as permittivity |
| D. | inversely as square root of conductivity |
| Answer» E. | |
| 534. |
In cellphone communication base antennas are connected to other base antennas in |
| A. | line of sight communication |
| B. | ionospheric propagation |
| C. | ground wave propagation |
| D. | medium wave propagation |
| Answer» B. ionospheric propagation | |
| 535. |
Which of the following is not between F2 layer and D layer? |
| A. | E layer |
| B. | F1 layer |
| C. | G region |
| D. | All of the above |
| Answer» D. All of the above | |
| 536. |
Radiation resistance for wire antenna is |
| A. | 55 Ω |
| B. | 65 Ω |
| C. | 100 Ω |
| D. | 377 Ω |
| Answer» C. 100 Œ© | |
| 537. |
The dimension of flux density is |
| A. | MT-1Q-1 |
| B. | MT-2 |
| C. | MT1Q1 |
| D. | MT-1Q-2 |
| Answer» B. MT-2 | |
| 538. |
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. | #NAME? |
| B. | #NAME? |
| C. | #NAME? |
| D. | #NAME? |
| Answer» D. #NAME? | |
| 539. |
The polarization of dielectric materials results in |
| A. | production of eddy currents |
| B. | creation of electric dipoles |
| C. | absorption of electrons |
| D. | release of high velocity protons |
| Answer» C. absorption of electrons | |
| 540. |
Bandwidth of an antenna is related with where Q is quality factor |
| A. | Q ‚àù B |
| B. | Q ‚àù 1/B |
| C. | Q ‚àù B2 |
| D. | Q ‚àù 1/B2 |
| Answer» C. Q ‚àù B2 | |
| 541. |
The effective length of an λ/2 antenna (Given Rr = 73 Ω and (Ae)max = 0.13 λ2 and η = 120 p is __________ . |
| A. | 0.6348 λ |
| B. | 0.317 λ |
| C. | 0.158 λ |
| D. | 0.371 λ |
| Answer» C. 0.158 Œª | |
| 542. |
The absorption of EM wave by the atmosphere depends on |
| A. | polarization of waves |
| B. | frequency in use |
| C. | dist. from Ty |
| D. | height of antenna |
| Answer» C. dist. from Ty | |
| 543. |
The wave propagation occurs without attenuation in case of a |
| A. | conductor |
| B. | semiconductor |
| C. | perfect dielectric |
| D. | none of the above |
| Answer» D. none of the above | |
| 544. |
An end fire array consisting of several half-wave lengths of directive gain 40, then array length will be |
| A. | 10 λ |
| B. | 100 λ |
| C. | 20 λ |
| D. | 5 λ |
| Answer» B. 100 Œª | |
| 545. |
The radio horizon for space waves is about three-fourth as for as the optical horizon. |
| A. | 1 |
| B. | |
| C. | small height antenna directly mounted on jeeps, ships, etc. |
| D. | the towers or masts which are used as radiators |
| Answer» C. small height antenna directly mounted on jeeps, ships, etc. | |
| 546. |
According to maximum power transfer theorem, if the load is inductive, the source should be |
| A. | inductive |
| B. | capacitive |
| C. | resistive |
| D. | any of the above |
| Answer» C. resistive | |
| 547. |
The sinusoidally time varying vector field is |
| A. | elliptically polarized |
| B. | circularly polarized |
| C. | linearly polarized |
| D. | unpolarized |
| Answer» E. | |
| 548. |
In a vertical earthed antenna the base input impedance will be inductive for a height |
| A. | between |
| B. | more than |
| C. | surface |
| D. | ground |
| Answer» C. surface | |
| 549. |
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) Œ© | |
| 550. |
The charges between a hollow and solid metal spheres reside |
| A. | through out in both |
| B. | on outer surface in hollow and through out in solid |
| C. | on the outer surface in both |
| D. | none of the above |
| Answer» D. none of the above | |