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.
| 201. |
The materials which become polarized on the application of mechanical stress are called piezoelectric. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 202. |
Assertion (A): Metals are better heat conductors than insulators.Reason (R): If is temperature gradient, Q is heat flow density and K is thermal conductivity, then Q = - K (dT/dx). |
| A. | A is true but R is false |
| B. | A is false but R is true |
| Answer» C. | |
| 203. |
Assertion (A): In many materials, dielectric polarization causes mechanical distortion.Reason (R): If dielectric polarization causes mechanical distortion then mechanical distortion must cause dielectric polarization. |
| 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 | |
| 204. |
The relative permeability of a ferromagnetic material is |
| A. | 1 |
| B. | less than 1 |
| C. | about 10 |
| D. | 1000 or more |
| Answer» E. | |
| 205. |
Automobile ignition systems use the principle of |
| A. | resistance |
| B. | self inductance |
| C. | mutual inductance |
| D. | capacitance |
| Answer» D. capacitance | |
| 206. |
The capacitance of a capacitor is not affected by |
| A. | ‚ààr |
| B. | distance between plates |
| Answer» C. | |
| 207. |
When subjected to alternating stresses, an insulating material is characterised by complex dielectric constant ‚àà'r - j‚àà"r . In such materials, the dielectric losses under alternating stress is proportional |
| A. | ‚àà'r |
| B. | (‚àà"r)2 |
| Answer» B. (‚àà"r)2 | |
| 208. |
When a dielectric is subjected to an electric field E, each volume element of dielectric can be considered to be carrying an electric dipole moment. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 209. |
In a conductor the current flow is due to |
| A. | holes |
| B. | electrons |
| C. | ions |
| D. | electrons and ions |
| Answer» C. ions | |
| 210. |
As regards ferromagnetic Curie temperature Qf and paramagnetic curie temperature θ |
| A. | θ equal to or less than Qf |
| B. | θ may be equal to less than or more Qf |
| Answer» C. | |
| 211. |
Assertion (A): If an electron having charge e is revolving in an orbit of radius R and with angular velocity ω, the magnetic dipole moment of orbit is 0.5 eωR2.Reason (R): Orbital angular momentum and magnetic dipole moment are always equal. |
| 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 | |
| 212. |
Which of the following is used in automatic control of street lights? |
| A. | Thermistor |
| B. | Photoconductor |
| C. | Transistor |
| D. | Varistor |
| Answer» C. Transistor | |
| 213. |
Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.Reason (R): Thermionic emission current ‚àù T2 e-Ew/kT. |
| A. | A is true but R is false |
| B. | A is false but R is true |
| Answer» B. A is false but R is true | |
| 214. |
The colour code on a carbon resistor is green-blue-yellow. The tolerance is |
| A. | ± 5% |
| B. | ± 10% |
| C. | ± 20% |
| D. | ± 30% |
| Answer» E. | |
| 215. |
Assertion (A): Acceptor extrinsic semiconductor has higher conductivity than intrinsic semiconductor.Reason (R): Addition of p-type impurity produces an allowable discrete energy level just above valence band. |
| A. | A is true but R is false |
| B. | A is false but R is true |
| Answer» B. A is false but R is true | |
| 216. |
As regards ‚àà0 and ‚ààr (absolute and relative permittivity) |
| A. | both ‚àà0 and ‚ààr can be interpreted in terms of atomic properties of medium |
| B. | only ‚ààr can be interpreted in terms of atomic properties of medium |
| C. | only ‚àà0 can be interpreted in terms of atomic properties |
| D. | ‚ààr has no physical significance |
| Answer» C. only ‚àà0 can be interpreted in terms of atomic properties | |
| 217. |
A dielectric is subjected to alternating field. The dielectric losses are potential to |
| A. | both real and imaginary parts of dielectric constant |
| B. | either real or imaginary part of dielectric constant |
| Answer» C. | |
| 218. |
Diamagnetic materials do not have permanent magnetic dipoles. |
| A. | 1 |
| B. | |
| C. | copper decreases and germanium increases |
| D. | both decreases |
| Answer» B. | |
| 219. |
Curie Weiss law is . |
| A. | 4, 1, 3, 2 |
| B. | 4, 1, 2, 3 |
| Answer» B. 4, 1, 2, 3 | |
| 220. |
Orbital magnetic dipole moment is due to the motion of electron in its orbit around nucleus. |
| 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. | |
| 221. |
Resistivity of copper is lower than that of nickel. When a small percentage of copper is added to nickel, the resistivity |
| A. | may increase or decrease |
| B. | remains the same |
| C. | 1 |
| D. | |
| Answer» B. remains the same | |
| 222. |
As the atoms of rare gases become larger, electronic polarizability |
| A. | increases |
| B. | decreases |
| C. | remains the same |
| D. | may increase or decrease |
| Answer» D. may increase or decrease | |
| 223. |
A rare gas has N atoms per m3. If electronic polarizability of single atom of this gas is ae, then |
| A. | ‚àà0(‚ààr - 1) = Nae |
| B. | ‚àà0(‚ààr - 2) = Nae |
| C. | 100 Ω |
| D. | 1000 Ω |
| Answer» D. 1000 Œ© | |
| 224. |
For small size high frequency coils, the most common core material is |
| A. | powdered iron |
| B. | steel |
| C. | 1 |
| D. | |
| Answer» B. steel | |
| 225. |
The materials having low retentivity are suitable for making |
| A. | temporary smagnets |
| B. | weak magnets |
| C. | permanent magnets |
| D. | both temporary and permanent magnets |
| Answer» B. weak magnets | |
| 226. |
As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times . |
| A. | 1 |
| B. | |
| C. | air core |
| D. | cast iron cored |
| Answer» B. | |
| 227. |
The units of polarization of dielectric are |
| A. | Cm |
| B. | |
| C. | towards positive terminal |
| Answer» B. | |
| 228. |
An electron in a homogeneous magnetic field and having velocity perpendicular to the direction of field moves |
| A. | along a straight line inclined at 45° to field |
| B. | in a circular path |
| C. | 1 |
| D. | |
| Answer» E. | |
| 229. |
In terms of Planck's constant h, the orbital angular momentum of an electron is |
| A. | covalent bonding |
| B. | recombination |
| C. | thermal energy |
| D. | free electrons |
| Answer» C. thermal energy | |
| 230. |
The most important primary force of attraction in the formation of solids is |
| A. | electromagnetic |
| B. | electrostatic |
| C. | quantum-electrostatic |
| D. | quantum electromagnetic |
| Answer» C. quantum-electrostatic | |
| 231. |
A capacitor can be represented by a capacitance and resistance in parallel. For a good capacitor, this parallel resistance should be |
| 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» E. | |
| 232. |
The application of magnetic field to superconducting material |
| A. | increases transition temperature |
| B. | decreases transition temperature |
| C. | has no effect on transition temperature |
| D. | may increase or decrease the transition temperature |
| Answer» C. has no effect on transition temperature | |
| 233. |
In solid insulator materials having only one kind of atom, the types of polarization which exist are |
| A. | electronic, ionic and permanent |
| B. | electronic and permanent |
| C. | linear equation |
| D. | differential equation |
| Answer» B. electronic and permanent | |
| 234. |
For a multiplate capacitor having n plates, A as area of each plate, the capacitance is proportional to |
| A. | (n + 1) A |
| B. | |
| C. | 1 and 3 only |
| Answer» C. 1 and 3 only | |
| 235. |
A permeable substance is one |
| A. | which is a good conductor |
| B. | through which magnetic lines of force can pass easily |
| C. | ‚àà"r |
| D. | both ‚àà'r and ‚àà"r |
| Answer» E. | |
| 236. |
Assertion (A): Copper is a good conductor of electricity.Reason (R): Copper has a face centred cubic lattice. |
| 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 | |
| 237. |
Ferromagnetic materials |
| A. | shows spontaneous magnetisation below a certain temperature |
| B. | have resistivity very high as compared to that of iron |
| C. | can be used even at microwave frequencies |
| D. | all of the above |
| Answer» E. | |
| 238. |
As per temperature limits, the number of categories of solid dielectrics are |
| A. | 8 |
| B. | 5 |
| C. | is almost equal to the number of valence electrons |
| D. | is about half the number of valence electrons |
| Answer» B. 5 | |
| 239. |
Assertion (A): Ferrites are very useful at very high frequencies.Reason (R): Ferrites have high permeability and high resistivity. |
| 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 | |
| 240. |
Figure shows a composite capacitor. If CA, CB, CC are the capacitances of capacitors A, B, C, the overall capacitance C is |
| A. | C = |
| B. | C = |
| C. | Qf > θ |
| D. | θ > Qf |
| Answer» D. Œ∏ > Qf | |
| 241. |
The temperature coefficient of resistivity of semiconductors is |
| A. | positive |
| B. | negative |
| C. | may be positive or negative |
| D. | very low |
| Answer» C. may be positive or negative | |
| 242. |
In its lowest state, the electron is bound to the field of proton by an energy equal to |
| A. | 13.6 eV |
| B. | 0.2 eV |
| C. | equal to applied field |
| D. | equal to applied field minus a contribution from neighbouring dipoles |
| Answer» D. equal to applied field minus a contribution from neighbouring dipoles | |
| 243. |
Assertion (A): If difference between static and optical dielectric constant is high, the mechanical compressiblity of that material is also high.Reason (R): For soft ions, ionic polarization per unit field is higher than that of hard ions. |
| 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 | |
| 244. |
The wavelength of light emitted by GaAs laser is 8670 x 10-10 m. If h = 6.626 x 10-34 Js, velocity of light = 3 x 108 m/s and eV = 1.602 x 10-19 J, the energy gap in GaAs is |
| A. | 0.18 eV |
| B. | 0.7 eV |
| C. | 1.43 eV |
| D. | 2.39 eV |
| Answer» D. 2.39 eV | |
| 245. |
In a pure sample of silicon |
| A. | the number of holes and free electrons is always equal |
| B. | the number of free electrons is more than the number of holes |
| C. | the number of free electrons and holes is equal at low temperature |
| D. | the number of free electrons is less than number of holes |
| Answer» B. the number of free electrons is more than the number of holes | |
| 246. |
Assertion (A): Dielectric constant is independent of temperature unless the temperature is extremely high.Reason (R): For normal temperatures the number of atoms per unit volume is constant. |
| 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 | |
| 247. |
Assertion (A): If WF is Fermi energy, v is velocity of electron and m is mass of electron, then .Reason (R): Conductivity of a metal depends on temperature and impurity concentration. |
| 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 | |
| 248. |
In an hydrogen atom, an electron moves in the field of a proton. The stability of orbit requires equilibrium between coulomb's force and centrifugal force. |
| A. | 1 |
| B. | |
| C. | air |
| D. | ferrite |
| Answer» B. | |
| 249. |
Above a certain temperature, the specific heat of a metal becomes constant. This temperature is called |
| A. | Debye temperature |
| B. | Curie temperature |
| C. | Neel temperature |
| D. | Transition temperature |
| Answer» B. Curie temperature | |
| 250. |
Iron has a body centred cubic structure. |
| A. | 1 |
| B. | |
| Answer» B. | |