MCQOPTIONS
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MCQOPTIONS
This section includes 595 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. |
Ferroelectric materials are those which |
| A. | cannot be polarized |
| B. | have a permanent polarization |
| C. | have ae equal to zero |
| D. | have μp = 0 |
| Answer» C. have ae equal to zero | |
| 452. |
The magnetic quantum number determines the component of angular momentum along a prescribed direction. |
| A. | 1 |
| B. | |
| C. | |
| Answer» B. | |
| 453. |
The carrier mobility in a semiconductor is 0.4 m2/Vs. Its diffusion constant at 300 K will be (in m2/s) |
| A. | 0.4 |
| B. | 0.16 |
| C. | 0.04 |
| D. | 0.01 |
| Answer» E. | |
| 454. |
Semi conducting materials are all |
| A. | elements |
| B. | compounds |
| C. | elements or compounds |
| D. | elements or mixtures |
| Answer» D. elements or mixtures | |
| 455. |
In metals, the average drift velocity of electron per unit field is called mobility. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 456. |
The units of μ0 and μr are |
| A. | H/m for both |
| B. | H/m for μr and no units for μ0 |
| C. | H/m for μ0 and no units for μr |
| D. | Wb/m for μ0 and no units for μr |
| Answer» D. Wb/m for Œº0 and no units for Œºr | |
| 457. |
At room temperature, the current in intrinsic semiconductor is due to |
| A. | holes |
| B. | electrons |
| C. | ions |
| D. | holes and electrons |
| Answer» E. | |
| 458. |
As per Matthiessen's rule, the total resistivity r of a conductor can be written as r = ri + aT, where ri and a are constants and T is absolute temperature. At very low temperatures |
| A. | aT = 0 |
| B. | aT > ri |
| C. | aT ∼ ri |
| D. | aT < ri |
| Answer» E. | |
| 459. |
As regards dielectric constant εr |
| A. | the units are farads/m |
| B. | the units are newton/coulomb |
| C. | it is dimensionless |
| D. | the units are farads |
| Answer» D. the units are farads | |
| 460. |
The core of a solenoid is made of material of relative permeability μr. A small cavity area dA and length dl is cut in the core. If it is desired that flux density in the cavity should be equal to B0 |
| A. | the fields inside and outside the cavity must be equal |
| B. | the field inside the cavity must be made stronger than field outside the cavity |
| C. | the field inside the cavity must be made weaker than the field outside the cavity |
| D. | none of the above |
| Answer» C. the field inside the cavity must be made weaker than the field outside the cavity | |
| 461. |
The relationship of hysteresis loss to maximum flux density was first determined by |
| A. | C. Steinmetz |
| B. | G.R. Kirchoff |
| C. | Mr. Laplace |
| D. | Mr. Ampere |
| Answer» B. G.R. Kirchoff | |
| 462. |
Assertion (A): Electronic and Ionic polarization in a polyatomic gas are independent of temperature.Reason (R): The orientation polarization is independent of temperature. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» D. A is false but R is true | |
| 463. |
Ferrites have |
| A. | a low copper loss |
| B. | low eddy current loss |
| C. | low resistivity |
| D. | higher specific gravity compared to iron |
| Answer» C. low resistivity | |
| 464. |
The iron core of a coil is removed so that it becomes an air cored coil. Its inductance will |
| A. | increase |
| B. | decrease |
| C. | remain the same |
| D. | may increase or decrease |
| Answer» C. remain the same | |
| 465. |
In a coaxial cable, braided copper is used for |
| A. | conductor |
| B. | shield |
| C. | dielectric |
| D. | jacket |
| Answer» C. dielectric | |
| 466. |
In a valence crystal, the valence electrons |
| A. | are not shared |
| B. | are shared between neighbouring atoms |
| C. | are shared by all atoms |
| D. | any of the above |
| Answer» C. are shared by all atoms | |
| 467. |
The colour code on a carbon resistor is red-red-black-silver. The value of resistor is |
| A. | 22000 Ω |
| B. | 2200 Ω |
| C. | 22 ± 5% Ω |
| D. | 22 ± 10% Ω |
| Answer» E. | |
| 468. |
In atomic physics, a state with l = 0 is called p state. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 469. |
Assertion (A): Holes are majority carriers in p type semiconductor.Reason (R): In p type semiconductor, the electrons produced by thermal agitation recombine with holes. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are true but R is not correct explanation of A | |
| 470. |
When Schrodinger equation is applied to the motion of electron in the field of protons, the physically acceptable solutions for the wave function exist for quantum number which are |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 5 |
| Answer» C. 4 | |
| 471. |
The number of turns in a coil is doubled. If initial time constant is T, the new time constant is |
| A. | T |
| B. | 2T |
| C. | 4T |
| Answer» C. 4T | |
| 472. |
Assertion (A): For Diamond, μr = 1Reason (R): Diamond is a diamagnetic material. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are true but R is not correct explanation of A | |
| 473. |
The equation D = ‚àà0‚ààr E refers only to isotropic materials. |
| A. | 1 |
| B. | |
| C. | hysteresis |
| D. | magnetostriction |
| Answer» B. | |
| 474. |
Assertion (A): In imperfect capacitors, the current does not lead the applied ac voltage by 90°.Reason (R): When subjected to ac fields, the dielectric constant can be expressed as ∈'r - j∈"r. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are true but R is not correct explanation of A | |
| 475. |
In carbon resistor colour code, if the third band is of silver, it indicates |
| A. | that three zeros are to be added to indicate the resistance value |
| B. | multiplier is 0.01 |
| C. | multiplier is 0.1 |
| D. | tolerance is ± 5% |
| Answer» C. multiplier is 0.1 | |
| 476. |
Which of the following are donor impurities? GoldPhosphorusBoronAntimonyArsenicInduim Select the correct answer using the following codes |
| A. | 1, 2, 3 |
| B. | 1, 2, 4, 6 |
| C. | 3, 4, 5, 6 |
| D. | 2, 4, 5 |
| Answer» E. | |
| 477. |
Assertion (A): From the slope of the line in Figure, we can find permanent dipole moment of the molecules.Reason (R): Total polarization of a polyatomic gas is given by P = N(ae + ai + μ2p / 3kT)E. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are true but R is not correct explanation of A | |
| 478. |
Debye temperature of metals is |
| A. | about 10 K |
| B. | about 200 K |
| C. | about 600 K |
| D. | about 2 K |
| Answer» C. about 600 K | |
| 479. |
Assertion (A): If E is available energy state eV and EF is Fermi level, then probability of energy state E being occupied = 0.5.Reason (R): . |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» C. A is true but R is false | |
| 480. |
Lines of magnetic field cannot intersect. |
| A. | 1 |
| B. | |
| C. | Both A and R are true and R is correct explanation of A |
| D. | Both A and R are true but R is not correct explanation of A |
| Answer» B. | |
| 481. |
Nichrome is used for |
| A. | overload line wires |
| B. | heater coils |
| C. | lamp filaments |
| D. | all of the above |
| Answer» C. lamp filaments | |
| 482. |
The most important set of specifications of transformer oil include |
| A. | dielectric strength and viscosity |
| B. | dielectric strength and flash point |
| C. | viscosity and flash point |
| D. | flash point and viscosity |
| Answer» B. dielectric strength and flash point | |
| 483. |
Carbon steel has a residual flux density of 1 Wb/m2. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 484. |
When a material becomes a superconductor, its resistivity becomes |
| A. | very small |
| B. | zero |
| C. | about 10% of normal value |
| D. | about 20% of normal value |
| Answer» C. about 10% of normal value | |
| 485. |
Which of the following is used in temperature alarm circuits? |
| A. | Thermistor |
| B. | Photoconductor |
| C. | Transistor |
| D. | Varistor |
| Answer» B. Photoconductor | |
| 486. |
The dipole moment per unit volume P as a function of E for an insulator is |
| A. | P = ‚àà0 E(‚ààr) |
| B. | P = ‚àà0 E |
| C. | P = ‚àà0(‚ààr - 1) E |
| D. | P = |
| Answer» D. P = | |
| 487. |
In Fermi-Dirac statistics, the probability of electron occupation of an energy level equal to Fermi level is |
| A. | 0 |
| B. | 0.25 |
| C. | 0.5 |
| D. | 1 |
| Answer» D. 1 | |
| 488. |
If e is the charge of an electron, R is the radius of its orbit and ω is the angular velocity of electron, the magnetic dipole moment μm of the orbit is |μm| = eωR2. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 489. |
The fact that domains exhibits spontaneous magnetisation is |
| A. | first hypothesis is of Curie |
| B. | second hypothesis is of Weiss |
| C. | Curie-Weiss law |
| D. | Boltzmann's statistics |
| Answer» C. Curie-Weiss law | |
| 490. |
As per Curie-Weiss law, the magnetic susceptibility of a material varies as |
| A. | T-2 |
| B. | |
| C. | T |
| Answer» C. T | |
| 491. |
The elements which become superconducting at extremely low temperatures are |
| A. | good conductors at room temperature |
| B. | ferromagnetic at room temperature |
| C. | relatively poor conductors at room temperature |
| D. | insulators at room temperature |
| Answer» D. insulators at room temperature | |
| 492. |
Nickel is a non-magnetic material. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 493. |
The classes of solid dielectrics are |
| A. | A, B, C, D, E, F, H |
| B. | A E B F H C D |
| C. | Y A E B F H C |
| D. | A E B F H C |
| Answer» D. A E B F H C | |
| 494. |
The induced magnetic dipole moment has a direction opposite to the applied magnetic field. |
| A. | 1 |
| B. | |
| C. | aE2 |
| D. | a2E |
| Answer» B. | |
| 495. |
The hysteresis phenomenon in ferromagnetic materials exists at all temperatures. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 496. |
Assertion (A): In an intrinsic semiconductor J = (μn x μp)eni.Reason (R): Intrinsic charge concentration ni at temperature T is given by ni2 = A0 T3 e-EG0/kT. |
| A. | Both A and R are true and R is correct explanation of A |
| B. | Both A and R are true but R is not correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» C. A is true but R is false | |
| 497. |
If k is Boltzmann's constant and T is absolute temp, then at room temp. |
| A. | kT 0.025 eV |
| B. | kT 0.5 eV |
| C. | kT 1 eV |
| D. | kT 100 eV |
| Answer» B. kT 0.5 eV | |
| 498. |
For dielectrics in alternating field, polarizability ae is a complex quantity. The imaginary part of ae is zero for |
| A. | ω = 0 |
| B. | ω → ∞ |
| C. | ω = 0 and ω → ∞ |
| D. | ω = natural frequency ω0 |
| Answer» D. œâ = natural frequency œâ0 | |
| 499. |
The probability of recombination of electrons and holes in a semiconductor is proportional to |
| A. | density of electrons |
| B. | density of holes |
| C. | density of electrons and holes |
| D. | none of the above |
| Answer» D. none of the above | |
| 500. |
The relaxation time of electrons in a metal is of the order of |
| A. | 10-6 secs |
| B. | 10-10 secs |
| C. | 10-14 secs |
| D. | 10-20 secs |
| Answer» D. 10-20 secs | |