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.
| 501. |
Which of these has lowest dielectric strength? |
| A. | Dry air |
| B. | Wet air |
| C. | Cotton |
| D. | Paper |
| Answer» C. Cotton | |
| 502. |
When temperature is above ferromagnetic Curie temperature, a ferromagnetic material |
| A. | becomes a paramagnetic material |
| B. | becomes a very strong ferromagnetic material |
| C. | becomes diamagnetic material |
| D. | none of the above |
| Answer» B. becomes a very strong ferromagnetic material | |
| 503. |
The dielectrics having only one kind of atoms are known as elemental dielectrics. |
| A. | 1 |
| B. | |
| C. | B = μr (H + M) |
| D. | B = μ0 (H + M) |
| Answer» B. | |
| 504. |
The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called |
| A. | Weiss temperature |
| B. | Curie temperature |
| C. | Neel temperature |
| D. | None of the above |
| Answer» D. None of the above | |
| 505. |
Assertion (A): For most metals, Fermi energy EF is less than 10 eV.Reason (R): Fermi level of a metal is given by EF = 3.64 x 10-19 (n)2/3 where n is number of free electrons/m3 of metal. |
| 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 | |
| 506. |
Yettrium-iron garnet (Y2Fe5O12) is a soft magnetic material suitable for applications involving |
| A. | dc |
| B. | 50 Hz ac |
| C. | ac of a few K Hz |
| D. | ac of a few hundred MHz |
| Answer» B. 50 Hz ac | |
| 507. |
In metals the valence electron wave functions are strongly perturbed by the presence of neighbouring atoms. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 508. |
The real part of complex dielectric constant and tanδ for a dielectric are 2.1 and 5 x 10-4 at 100 Hz respectively. The imaginary part of dielectric constant at 100 Hz is |
| A. | 1.05 x 10-3 |
| B. | 2.1 x 10-3 |
| C. | 5 x 10-3 |
| D. | 1.05 x 10-2 |
| Answer» B. 2.1 x 10-3 | |
| 509. |
As the temperature of semiconductor is increased |
| A. | the average number of free charge carriers decreases |
| B. | the average number of free charge carriers increases |
| C. | the average number of free charge carriers remains the same |
| D. | the average number of free charge carriers may increase or decrease |
| Answer» C. the average number of free charge carriers remains the same | |
| 510. |
Assertion (A): Hall effect is used to determine whether the semi- conductor is p or n type.Reason (R): Under the influence of field, holes and electrons move in opposite direction. |
| 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 | |
| 511. |
A characteristic property of crystal is its periodicity of structure. |
| A. | 1 |
| B. | |
| C. | Bmax |
| D. | B1.6max |
| Answer» B. | |
| 512. |
The temperature coefficient of a thermistor |
| A. | is positive |
| B. | is negative |
| C. | zero |
| D. | may be positive or negative depending on its composition |
| Answer» C. zero | |
| 513. |
Hydrogen is used in |
| A. | large size transformers |
| B. | MCB |
| C. | large size generators |
| D. | circuit breakers |
| Answer» D. circuit breakers | |
| 514. |
If there are no permanent dipoles in a dielectric material, the dielectric constant is independent of temperature. |
| 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. | |
| 515. |
Assertion (A): In a perfect capacitor, the current density is given by ω ∈0E0∈'rcos(ωt + 90°), where ∈r' is real part of dielectric constant.Reason (R): In a perfect capacitor, dielectric losses are zero. |
| 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 | |
| 516. |
For a permanent magnetic material |
| A. | the residual induction and coercive field should be large |
| B. | the residual induction and coercive field should be small |
| C. | area of hysteresis loop should be small |
| D. | initial relative permeability should be high |
| Answer» B. the residual induction and coercive field should be small | |
| 517. |
If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of |
| A. | 1 |
| B. | -1 |
| C. | 0 |
| D. | 3 |
| Answer» B. -1 | |
| 518. |
Assertion (A): If an atom of polarizability a is placed in homogeneous field E, the energy stored is 0.5 aE2.Reason (R): Capacitance of an isolated conducting sphere R in vacuum is 4 p‚àà0 R farads. |
| 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 | |
| 519. |
A leakage capacitor can be represented by a capacitance C and resistance R in parallel C. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 520. |
Material which lack permanent magnetic dipoles are known as |
| A. | paramagnetic |
| B. | diamagnetic |
| C. | ferromagnetic |
| D. | ferrimagnetic |
| Answer» C. ferromagnetic | |
| 521. |
If the temperature of an extrinsic semiconductor is increased so that the intrinsic carrier concentration is doubled, then |
| A. | the majority carrier density is doubled |
| B. | the minority carrier density is doubled |
| C. | the minority carrier density becomes 4 times the original value |
| D. | both the majority and minority carrier densities double |
| Answer» E. | |
| 522. |
A leaky dielectric has ‚ààr = ‚ààr' - j‚ààr". If a field E is applied, the current component in phase with E is proportional to ‚ààr". |
| 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. | |
| 523. |
Assertion (A): An electron having charge - e and mass m and lying in an electric field E is subjected to an acceleration - (e/m) E.Reason (R): If there are n electrons/m3 moving with velocity vx and each electron has a charge - e, the current density J = - n evx. |
| 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 | |
| 524. |
Assertion (A): Ferroelectric materials have spontaneous polarization.Reason (R): Above curie temperature, ‚àà = for ferro-electric materials. |
| 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 | |
| 525. |
If the number of atoms per unit volume of a monoatomic gas changes, the dielectric constant still remains constant. |
| A. | 1 |
| B. | |
| C. | 2 |
| D. | 9 |
| Answer» B. | |
| 526. |
In molecules of ionic crystals, orientation polarization is zero. |
| 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. | |
| 527. |
Hysteresis curve is associated with motion of domain walls. |
| A. | 1 |
| B. | |
| C. | 4 |
| D. | 16 |
| Answer» B. | |
| 528. |
Some ceramic materials become superconducting |
| A. | below liquid helium temperature |
| B. | between liquid helium and liquid nitrogen temperature |
| C. | above liquid nitrogen but below room temperature |
| D. | at room temperature |
| Answer» B. between liquid helium and liquid nitrogen temperature | |
| 529. |
If a sample of germanium and a sample of silicon have the same impurity density and are kept at room temperature |
| A. | both will have equal value of resistivity |
| B. | both will have equal negative resistivity |
| C. | resistivity of germanium will be higher than that of silicon |
| D. | resistivity of silicon will be higher than that of germanium |
| Answer» E. | |
| 530. |
If ω0 is the angular frequency of rotation of electron in the absence of magnetic field, the angular frequency ω, when a magnetic field B is acting is ω ≅ ω0 + (e/2m)B. |
| A. | 1 |
| B. | |
| C. | low |
| D. | very low |
| Answer» B. | |
| 531. |
The resistivity of intrinsic semiconductors, at room temperature, is of the order of |
| A. | 1 Ω-m |
| B. | 1000 Ω-m |
| C. | 106 Ω-m |
| D. | 10-3 Ω-m |
| Answer» B. 1000 Œ©-m | |
| 532. |
Assertion (A): The optical dielectric constant (i.e., εr at optical frequencies)of ionic dielectrics is less than static dielectric constant. Reason (R): At optical frequencies, Pi = 0. |
| 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 | |
| 533. |
The core of a coil has a length of 10 cm. The self inductance is 8 mH. If the core length is doubled, all other quantities remaining the same, the self inductance will be |
| A. | 32 mH |
| B. | 16 mH |
| C. | 8 mH |
| D. | 4 mH |
| Answer» E. | |
| 534. |
Soft iron is suitable for making temporary magnets. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 535. |
The law J = σE, where J is current density, σ is electrical conductivity and E is field strength is |
| A. | Ohm's law |
| B. | Gauss law |
| C. | Ampere's law |
| D. | Biot-Savart law |
| Answer» B. Gauss law | |
| 536. |
Thermistor is used in |
| A. | temperature measurement |
| B. | temperature control |
| C. | high temperature alarm circuits of devices |
| D. | all of the above |
| Answer» E. | |
| 537. |
In a true valence crystal, the bonding between the atoms is accomplished by the sharing of valence electrons. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 538. |
Assertion (A): A capacitor with imperfect dielectric can be represented by a capacitance in parallel with resistance.Reason (R): For imperfect dielectrics, dielectric constant has real and imaginary parts. |
| 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 | |
| 539. |
In the wave mechanical theory, the maximum of the charge distribution in the ground state occurs for a distance from the nucleus equal to |
| A. | first Bohr radius |
| B. | second Bohr radius |
| C. | third Bohr radius |
| D. | either first or second Bohr radius |
| Answer» B. second Bohr radius | |
| 540. |
Assertion (A): Power loss in a conductor of resistance P = I2R.Reason (R): When a conductor is carrying current with current density J as a result of applied field E, then heat developed/m3/ second = JE. |
| 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 | |
| 541. |
The number of valence electrons in donor impurity are |
| A. | 5 |
| B. | 4 |
| C. | 3 |
| D. | 1 |
| Answer» B. 4 | |
| 542. |
Assertion (A): Magnetic susceptibility of diamagnetic materials is much less than that of paramagnetic materials.Reason (R): For diamagnetic as well as paramagnetic materials, μr is nearly equal to 1. |
| 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 | |
| 543. |
Fleming's left hand rule is used to find |
| A. | direction of force on a current carrying conductor |
| B. | direction of flux in solenoid |
| C. | direction of magnetic field due to a current carrying conductor |
| D. | direction of induced emf |
| Answer» B. direction of flux in solenoid | |
| 544. |
Semiconductors have a positive temperature coefficient of resistivity. |
| A. | 1 |
| B. | |
| C. | D0 = Di |
| Answer» C. D0 = Di | |
| 545. |
A copper atom is neutral. Its core has a net charge of |
| A. | 0 |
| B. | 1 |
| C. | -1 |
| D. | 2 |
| Answer» C. -1 | |
| 546. |
With increase in temperature, the electrical conductivity would |
| A. | increase in metals as well as in intrinsic semiconductor |
| B. | increase in metals but decrease in intrinsic semiconductor |
| C. | decrease in metals but increase in intrinsic semiconductor |
| D. | decrease in metals as well as in intrinsic semiconductor |
| Answer» D. decrease in metals as well as in intrinsic semiconductor | |
| 547. |
On the basis of the type of chemical bonds, solids may be classified into |
| A. | ionic crystals |
| B. | ionic and valence crystals |
| C. | ionic crystal, valence crystals and metals |
| D. | ionic crystals, valence crystals, metal and vander wall crystals |
| Answer» E. | |
| 548. |
There is no hysteresis phenomenon is any dielectric material. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 549. |
The direction of force an a conductor carrying current and lying in a magnetic field can be found by using |
| A. | Fleming's left hand rule |
| B. | Fleming's right hand rule |
| C. | Cork screw rule |
| D. | Any of the above |
| Answer» B. Fleming's right hand rule | |
| 550. |
In a virgin specimen of iron, the direction of spontaneous magnetisation varies from domain to domain. |
| A. | 1 |
| B. | |
| C. | Thermistor |
| D. | Photoconductor |
| Answer» B. | |