McqMate
| 301. |
Acharge which when placed in vacuum from an equal and similar charge repels with a force of 9 x 10 N, is known as |
| A. | milli-coulomb |
| B. | micro-coulomb |
| C. | pico-coulomb |
| D. | coulomb |
| Answer» B. micro-coulomb | |
| 302. |
Dielectric strength of a medium is usually expressed in |
| A. | j/mm |
| B. | c/m2 |
| C. | kv/mm |
| D. | n/mm |
| Answer» C. kv/mm | |
| 303. |
A positive and a negative charge are initially 50 mm apart. When they are moved close together so that they are now only 10 mm apart, the force between them will be |
| A. | 5 times smaller than before |
| B. | 5 times greater than before |
| C. | 10 times greater than before |
| D. | 25 times larger than before |
| Answer» D. 25 times larger than before | |
| 304. |
Which is the most superior dielectric out of the following ? |
| A. | air |
| B. | glass |
| C. | bakelite |
| D. | paper |
| Answer» C. bakelite | |
| 305. |
When a dielectric is placed in an electric field the field strength |
| A. | decreases |
| B. | increases |
| C. | reduces to zero |
| D. | remain unchanged |
| Answer» A. decreases | |
| 306. |
To prevent the generation of static charges on rubber or flat leather |
| A. | surface is moistened |
| B. | conductive dressing is done |
| C. | oil compound dressing is done |
| D. | talcum powder is sprayed on the surface |
| Answer» B. conductive dressing is done | |
| 307. |
Which of the following capacitor is preferred in case of single phase motor ? |
| A. | mica capacitor |
| B. | paper capacitor |
| C. | electrolytic capacitor |
| D. | ceramic capacitor |
| Answer» C. electrolytic capacitor | |
| 308. |
A capacitance is a circuit component that opposes the change in circuit |
| A. | current |
| B. | voltage |
| C. | impedance |
| D. | none of the above |
| Answer» A. current | |
| 309. |
A condenser suitable for D.C. only is |
| A. | metallic plate variable gang condenser |
| B. | metallic paper capacitor |
| C. | oil impregrated paper condenser |
| D. | poled aluminium electrolytic condenser |
| Answer» D. poled aluminium electrolytic condenser | |
| 310. |
In a capacitor, the electric charge is stored in |
| A. | metal plates |
| B. | dielectric |
| C. | dielectric as well as metal plates |
| D. | none of the above |
| Answer» B. dielectric | |
| 311. |
Tesla is a unit of |
| A. | field strength |
| B. | inductance |
| C. | flux density |
| D. | flux |
| Answer» C. flux density | |
| 312. |
The materials having low retentivity are suitable for making |
| A. | weak magnets |
| B. | temporary magnets |
| C. | permanent magnets |
| D. | none of the above |
| Answer» B. temporary magnets | |
| 313. |
A magnetic field exists around |
| A. | iron |
| B. | copper |
| C. | aluminium |
| D. | moving charges |
| Answer» D. moving charges | |
| 314. |
Ferrites are materials. |
| A. | paramagnetic |
| B. | diamagnetic |
| C. | ferromagnetic |
| D. | none of the above |
| Answer» C. ferromagnetic | |
| 315. |
Air gap has eluctance as compared to iron or steel path |
| A. | little |
| B. | lower |
| C. | higher |
| D. | zero |
| Answer» B. lower | |
| 316. |
The direction of magnetic lines of force is |
| A. | from south pole to north pole |
| B. | from north pole to south pole |
| C. | from one end of the magnet to another |
| D. | none of the above |
| Answer» B. from north pole to south pole | |
| 317. |
Which of the following is a vector quantity ? |
| A. | relative permeability |
| B. | magnetic field intensity |
| C. | flux density |
| D. | magnetic potential |
| Answer» B. magnetic field intensity | |
| 318. |
The two conductors of a transmission line carry equal current I in opposite directions. The force on each conductor is |
| A. | proportional to 7 |
| B. | proportional to x |
| C. | proportional to distance between the conductors |
| D. | inversely proportional to i |
| Answer» B. proportional to x | |
| 319. |
A material which is slightly repelled by a magnetic field is known as |
| A. | ferromagnetic material |
| B. | diamagnetic material |
| C. | paramag>etic material |
| D. | conducting material |
| Answer» B. diamagnetic material | |
| 320. |
When an iron piece is placed in a magnetic field |
| A. | the magnetic lines of force will bend away from their usual paths in order to go away from the piece |
| B. | the magnetic lines of force will bend away from their usual paths in order to pass through the piece |
| C. | the magnetic field will not be affected |
| D. | the iron piece will break |
| Answer» B. the magnetic lines of force will bend away from their usual paths in order to pass through the piece | |
| 321. |
Fleming's left hand rule is used to find |
| A. | direction of magnetic field due to current carrying conductor |
| B. | direction of flux in a solenoid |
| C. | direction of force on a current car¬rying conductor in a magnetic field |
| D. | polarity of a magnetic pole |
| Answer» C. direction of force on a current car¬rying conductor in a magnetic field | |
| 322. |
The ratio of intensity of magnetisation to the magnetisation force is known as |
| A. | flux density |
| B. | susceptibility |
| C. | relative permeability |
| D. | none of the above |
| Answer» B. susceptibility | |
| 323. |
The left hand rule correlates to |
| A. | current, induced e.m.f. and direc¬tion of force on a conductor |
| B. | magnetic field, electric field and direction of force on a conductor |
| C. | self induction, mutual induction and direction of force on a conductor |
| D. | current, magnetic field and direc¬tion of force on a conductor |
| Answer» D. current, magnetic field and direc¬tion of force on a conductor | |
| 324. |
The unit of relative permeability is |
| A. | henry/metre |
| B. | henry |
| C. | henry/sq. m |
| D. | it is dimensionless |
| Answer» D. it is dimensionless | |
| 325. |
A conductor of length L has current I passing through it, when it is placed parallel to a magnetic field. The force experienced by the conductor will be |
| A. | zero |
| B. | bli |
| C. | b2li |
| D. | bli2 |
| Answer» A. zero | |
| 326. |
The force between two long parallel conductors is inversely proportional to |
| A. | radius of conductors |
| B. | current in one conductor |
| C. | product of current in two conduc¬tors |
| D. | distance between the conductors |
| Answer» D. distance between the conductors | |
| 327. |
Materials subjected to rapid reversal of magnetism should have |
| A. | large area oib-h loop |
| B. | high permeability and low hysteresis loss |
| C. | high co-ercivity and high reten-tivity |
| D. | high co-ercivity and low density |
| Answer» B. high permeability and low hysteresis loss | |
| 328. |
The main constituent of permalloy is |
| A. | cobalt |
| B. | chromium |
| C. | nickel |
| D. | tungsten |
| Answer» C. nickel | |
| 329. |
Paramagnetic materials have relative permeability |
| A. | slightly less than uuity |
| B. | equal to unity |
| C. | slightly more than unity |
| D. | equal to that ferromagnetic mate rials |
| Answer» C. slightly more than unity | |
| 330. |
Substances which have permeability less than the permeability of free space are known as |
| A. | ferromagnetic |
| B. | paramagnetic |
| C. | diamagnetic |
| D. | bipolar |
| Answer» C. diamagnetic | |
| 331. |
Two infinitely long parallel conductors in vacuum anf' separated 1 metre between centres >rhen a current of 1 ampere flows thn. ugh each conductor, produce on each otLer a force of |
| A. | 2 x 1(t2 n/m) |
| B. | 2 x kt3 n/m |
| C. | 2 x 10"5 n/m |
| D. | 2x 1(t7 n/m) |
| Answer» D. 2x 1(t7 n/m) | |
| 332. |
In the left hand rule, forefinger always represents |
| A. | voltage |
| B. | current |
| C. | magnetic field |
| D. | direction of force on the conductor |
| Answer» C. magnetic field | |
| 333. |
Which of the following is a ferromagnetic material ? |
| A. | tungsten |
| B. | aluminium |
| C. | copper |
| D. | nickel |
| Answer» D. nickel | |
| 334. |
Ferrites are a sub-group of |
| A. | non-magnetic materials |
| B. | ferro-magnetic materials |
| C. | paramagnetic materials |
| D. | ferri-magnetic materials |
| Answer» D. ferri-magnetic materials | |
| 335. |
Gilbert is a unit of |
| A. | electromotive force |
| B. | magnetomotive force |
| C. | conductance |
| D. | permittivity |
| Answer» B. magnetomotive force | |
| 336. |
The working of a meter is based on the use of a permanent magnet. In order to protect the meter functioning from stray magnetic fields |
| A. | meter is surrounded by strong magnetic fields |
| B. | a soft iron shielding is used |
| C. | a plastic shielding is provided |
| D. | a shielding of anon-magnetic material is used |
| Answer» B. a soft iron shielding is used | |
| 337. |
Reciprocal of permeability is |
| A. | reluctivity |
| B. | susceptibility |
| C. | permittivity |
| D. | conductance |
| Answer» A. reluctivity | |
| 338. |
The relative permeability is less than unity is case of |
| A. | ferromagnetic materials |
| B. | ferrites |
| C. | non-ferrous materials |
| D. | diamagnetic materials |
| Answer» D. diamagnetic materials | |
| 339. |
Which of the following is the unit of magnetic flux density ? |
| A. | weber |
| B. | lumens |
| C. | tesla |
| D. | none of the above |
| Answer» C. tesla | |
| 340. |
The magnetism left in the iron after exciting field has been removed is known as |
| A. | permeance |
| B. | residual magnetism |
| C. | susceptance |
| D. | reluctance |
| Answer» B. residual magnetism | |
| 341. |
Which of the following is not a unit of flux? |
| A. | maxwell |
| B. | telsa |
| C. | weber |
| D. | all of the above |
| Answer» B. telsa | |
| 342. |
Which of the following is expected to have the maximum permeability ? |
| A. | brass |
| B. | copper |
| C. | zinc |
| D. | ebonite |
| Answer» D. ebonite | |
| 343. |
One telsa is equal to |
| A. | 1 wb/mm2 |
| B. | 1 wb/m |
| C. | 1 wb/m2 |
| D. | 1 mwb/m2 |
| Answer» C. 1 wb/m2 | |
| 344. |
Out of the following statements, concerning an electric field, which statement is not true ? |
| A. | the electric intensity is a vector quantity |
| B. | the electric field intensity at a point is numerically equal to the force exerted upon a charge placed at that point |
| C. | an electric field is defined as a point in space at which an electric charge would experienc* a force |
| D. | unit field intensity in the exertion of a force of one newton on a charge of one coulomb |
| Answer» B. the electric field intensity at a point is numerically equal to the force exerted upon a charge placed at that point | |
| 345. |
When a magnet is in motion relative to a coil the induced e.m.f. does not depend upon |
| A. | resistance of the coil |
| B. | motion of the magnet |
| C. | number of turns of the coil |
| D. | pole strength of the magnet |
| Answer» A. resistance of the coil | |
| 346. |
One maxwell is equal to |
| A. | 10 webers |
| B. | 10 webers |
| C. | 10 webers |
| D. | 10 webers |
| Answer» D. 10 webers | |
| 347. |
When two ends of a circular uniform wire are joined to the terminals of a battery, the field at the centre of the circle |
| A. | will be zero |
| B. | will be infinite |
| C. | will depend on the amount of e.m.f. applied |
| D. | will depend on the radius of the circle |
| Answer» D. will depend on the radius of the circle | |
| 348. |
Susceptibility is positive for |
| A. | non-magnetic substances |
| B. | diamagnetic substances |
| C. | ferromagnetic substances |
| D. | none of the above |
| Answer» C. ferromagnetic substances | |
| 349. |
Two long parallel conductors carry 100 A. If the conductors are separated by 20 mm, the force per metre of length of each conductor will be |
| A. | 100 n |
| B. | 10 n |
| C. | 1 n |
| D. | 0.1 n |
| Answer» D. 0.1 n | |
| 350. |
The electromagnet has 50 turns and a current of 1A flows through the coil. If the length of the magnet circuit is 200 mm, what is the magnetic field strength ? |
| A. | 2500 at/m |
| B. | 250 at/m |
| C. | 25 at/m |
| D. | 2.5 at/m |
| Answer» B. 250 at/m | |
| 351. |
A square cross-sectional magnet has a pole strength of 1 x 10 Wb and cross sectional area of 20 mm x 20 mm. What is the strength at a distance of 100 mm from the unit pole in air ? |
| A. | 63.38 n/wb |
| B. | 633.8 n/wb |
| C. | 6338 n/wb |
| D. | 63380 n/wb |
| Answer» C. 6338 n/wb | |
| 352. |
The unit of flux is the same as that of |
| A. | reluctance |
| B. | resistance |
| C. | permeance |
| D. | pole strength |
| Answer» D. pole strength | |
| 353. |
Unit for quantity of electricity is |
| A. | ampere-hour |
| B. | watt |
| C. | joule |
| D. | coulomb |
| Answer» D. coulomb | |
| 354. |
The Biot-savart's law is a general modification of |
| A. | kirchhoffs law |
| B. | lenz\s law |
| C. | ampere\s law |
| D. | faraday\s laws |
| Answer» C. ampere\s law | |
| 355. |
The most effective and quickest may of making a magnet from soft iron is by |
| A. | placing it inside a coil carrying current |
| B. | induction |
| C. | the use of permanent magnet |
| D. | rubbing with another magnet |
| Answer» A. placing it inside a coil carrying current | |
| 356. |
The commonly used material for shielding or screening magnetism is |
| A. | copper |
| B. | aluminium |
| C. | soft iron |
| D. | brass |
| Answer» C. soft iron | |
| 357. |
If a copper disc is rotated rapidly below a freely suspended magnetic needle, the magnetic needle shall start rotating with a velocity |
| A. | less than that of disc but in opposite direction |
| B. | equal to that of disc and in the same direction |
| C. | equal to that of disc and in the opposite direction |
| D. | less than that of disc and in the same direction |
| Answer» D. less than that of disc and in the same direction | |
| 358. |
A permanent magnet |
| A. | attracts some substances and repels others |
| B. | attracts all paramagnetic substan¬ces and repels others |
| C. | attracts only ferromagnetic sub¬stances |
| D. | attracts ferromagnetic substances and repels all others |
| Answer» A. attracts some substances and repels others | |
| 359. |
The retentivity (a property) of material is useful for the construction of |
| A. | permanent magnets |
| B. | transformers |
| C. | non-magnetic substances |
| D. | electromagnets |
| Answer» A. permanent magnets | |
| 360. |
The relative permeability of materials is not constant. |
| A. | diamagnetic |
| B. | paramagnetic |
| C. | ferromagnetic |
| D. | insulating |
| Answer» C. ferromagnetic | |
| 361. |
The materials are a bit inferior conductors of magnetic flux than air. |
| A. | ferromagnetic |
| B. | paramagnetic |
| C. | diamagnetic |
| D. | dielectric |
| Answer» C. diamagnetic | |
| 362. |
Hysteresis loop in case of magnetically hard materials is more in shape as compared to magnetically soft materials. |
| A. | circular |
| B. | triangular |
| C. | rectangular |
| D. | none of the above |
| Answer» C. rectangular | |
| 363. |
A keeper is used to |
| A. | change the direction of magnetic lines |
| B. | amplify flux |
| C. | restore lost flux |
| D. | provide a closed path for flux |
| Answer» D. provide a closed path for flux | |
| 364. |
The change of cross-sectional area of conductor in magnetic field will affect |
| A. | reluctance of conductor |
| B. | resistance of conductor |
| C. | (a) and (b) b >th in the same way |
| D. | none of the above |
| Answer» C. (a) and (b) b >th in the same way | |
| 365. |
The uniform magnetic field is |
| A. | the field of a set of parallel conductors |
| B. | the field of a single conductor |
| C. | the field in which all lines of mag¬netic flux are parallel and equidis¬tant |
| D. | none of the above |
| Answer» C. the field in which all lines of mag¬netic flux are parallel and equidis¬tant | |
| 366. |
The magneto-motive force is |
| A. | the voltage across the two ends of exciting coil |
| B. | the flow of an electric current |
| C. | the sum of all currents embraced by one line of magnetic field |
| D. | the passage of magnetic field through an exciting coil |
| Answer» C. the sum of all currents embraced by one line of magnetic field | |
| 367. |
What will be the current passing through the ring shaped air cored coil when number of turns is 800 and ampere turns are 3200 ? |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» B. 4 | |
| 368. |
What will be the magnetic potential difference across the air gap of 2 cm length in magnetic field of 200 AT/m ? |
| A. | 2 at |
| B. | 4 at |
| C. | 6 at |
| D. | 10 at |
| Answer» B. 4 at | |
| 369. |
The initial permeability of an iron rod is |
| A. | the highest permeability of the iron rod |
| B. | the lowest permeability of the iron rod |
| C. | the permeability at the end of the iron rod |
| D. | the permeability almost in non-magnetised state |
| Answer» D. the permeability almost in non-magnetised state | |
| 370. |
How does the magnetic compass needle behave in a magnetic field ? |
| A. | it assures a position right angle to magnetic field |
| B. | it starts rotating |
| C. | it assures a position which follows a line of magnetic flux |
| D. | none of the above |
| Answer» C. it assures a position which follows a line of magnetic flux | |
| 371. |
The stray line of magnetic flux is defined as |
| A. | a line vertical to the flux lines |
| B. | the mean length of a ring shaped coil |
| C. | a line of magnetic flux in a non-uniform field |
| D. | a line of magnetic flux which does not follow the designed path |
| Answer» D. a line of magnetic flux which does not follow the designed path | |
| 372. |
The bar magnet has |
| A. | the dipole moment |
| B. | monopole moment |
| C. | (a) and (b) both |
| D. | none of the above |
| Answer» A. the dipole moment | |
| 373. |
Which of the following materials are dia-magnetic ? |
| A. | silver |
| B. | copper |
| C. | silver and copper |
| D. | iron |
| Answer» C. silver and copper | |
| 374. |
Which of the following type of materials are not very important for engineering applications ? |
| A. | ferromagnetic |
| B. | paramagnetic |
| C. | diamagnetic |
| D. | none of the above |
| Answer» C. diamagnetic | |
| 375. |
The susceptibility of paramagnetic materials generally lies between |
| A. | kt3 and 1ct6 |
| B. | 1ct3 and 1ct7 |
| C. | kt4 and kt8 |
| D. | 10"2 and kt5 |
| Answer» A. kt3 and 1ct6 | |
| 376. |
For which of the following materials the net magnetic moment should be zero ? |
| A. | diamagnetic materials |
| B. | ferrimagnetic materials |
| C. | antiferromagnetic materials |
| D. | antiferrimagnetic materials |
| Answer» C. antiferromagnetic materials | |
| 377. |
The attraction capacity of electromagnet will increase if the |
| A. | core length increases i |
| B. | core area increases |
| C. | flux density decreases |
| D. | flux density increases |
| Answer» D. flux density increases | |
| 378. |
Which of the following statements is correct ? |
| A. | the conductivity of ferrites is better than ferromagnetic materials |
| B. | the conductivity of ferromagnetic materials is better than ferrites |
| C. | the conductivity of ferrites is very high |
| D. | the conductivity of ferrites is same as that of ferromagnetic materials |
| Answer» A. the conductivity of ferrites is better than ferromagnetic materials | |
| 379. |
Temporary magnets are used in |
| A. | loud-speakers |
| B. | generators |
| C. | motors |
| D. | all of the above |
| Answer» D. all of the above | |
| 380. |
Main causes of noisy solenoid are |
| A. | strong tendency of fan out of lami-nations at the end caused by repul¬sion among magnetic lines of force |
| B. | uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts |
| C. | both of above |
| D. | none of the above |
| Answer» C. both of above | |
| 381. |
Magnetism of a magnet can be destroyed by |
| A. | heating |
| B. | hammering |
| C. | by inductive action of another magnet |
| D. | by all above methods |
| Answer» D. by all above methods | |
| 382. |
An air gap is usually inserted in magnetic circuits to |
| A. | increase m.m.f. |
| B. | increase the flux |
| C. | prevent saturation |
| D. | none of the above |
| Answer» C. prevent saturation | |
| 383. |
The relative permeability of a ferromagnetic material is |
| A. | less than one |
| B. | more than one |
| C. | more than 10 |
| D. | more than 100 or 1000 |
| Answer» D. more than 100 or 1000 | |
| 384. |
The unit of magnetic flux is |
| A. | henry |
| B. | weber |
| C. | ampereturn/weber |
| D. | ampere/metre |
| Answer» B. weber | |
| 385. |
Permeability in a magnetic circuit corresponds to in an electric circuit. |
| A. | resistance |
| B. | resistivity |
| C. | conductivity |
| D. | conductance |
| Answer» C. conductivity | |
| 386. |
Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it |
| A. | lowers their power efficiency |
| B. | increases their cost of manufacture |
| C. | leads to their increased weight |
| D. | produces fringing |
| Answer» A. lowers their power efficiency | |
| 387. |
Relative permeability of vacuum is |
| A. | 1 |
| B. | 1 h/m |
| C. | 1/4ji |
| D. | 4n x 10-\ h/m |
| Answer» A. 1 | |
| 388. |
Permanent magnets are normally made of |
| A. | alnico alloys |
| B. | aluminium |
| C. | cast iron |
| D. | wrought iron |
| Answer» A. alnico alloys | |
| 389. |
Those magnetic materials are best suited for making armature and transformer cores which have permeability and hystersis loss. |
| A. | high, high |
| B. | low, high |
| C. | high, low |
| D. | low, low |
| Answer» C. high, low | |
| 390. |
The rate of rise of current through an inductive coil is maximum |
| A. | at 63.2% of its maximum steady value |
| B. | at the start of the current flow |
| C. | after one time constant |
| D. | near the final maximum value of current |
| Answer» B. at the start of the current flow | |
| 391. |
When both the inductance and resistance of a coil are doubled the value of |
| A. | time constant remains unchanged |
| B. | initial rate of rise of current is doubled |
| C. | final steady current is doubled |
| D. | time constant is halved |
| Answer» A. time constant remains unchanged | |
| 392. |
A material for good magnetic memory should have |
| A. | low hysteresis loss |
| B. | high permeability |
| C. | low retentivity |
| D. | high retentivity |
| Answer» D. high retentivity | |
| 393. |
Conductivity is analogous to |
| A. | retentivity |
| B. | resistivity |
| C. | permeability |
| D. | inductance |
| Answer» C. permeability | |
| 394. |
In a magnetic material hysteresis loss takes place primarily due to |
| A. | rapid reversals of its magnetisation |
| B. | flux density lagging behind magnetising force |
| C. | molecular friction |
| D. | it high retentivity |
| Answer» D. it high retentivity | |
| 395. |
Those materials are well suited for making permanent magnets which have retentivity and coercivity. |
| A. | low, high |
| B. | high, high |
| C. | high, low |
| D. | low, low |
| Answer» B. high, high | |
| 396. |
If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be |
| A. | zero |
| B. | small |
| C. | large |
| D. | none of the above |
| Answer» C. large | |
| 397. |
Hard steel is suitable for making permanent magnets because |
| A. | it has good residual magnetism |
| B. | its hysteresis loop has large area |
| C. | its mechanical strength is high |
| D. | its mechanical strength is low |
| Answer» A. it has good residual magnetism | |
| 398. |
Silicon steel is used in electrical machines because it has |
| A. | low co-ercivity |
| B. | low retentivity |
| C. | low hysteresis loss |
| D. | high co-ercivity |
| Answer» C. low hysteresis loss | |
| 399. |
Conductance is analogous to |
| A. | permeance |
| B. | reluctance |
| C. | flux |
| D. | inductance |
| Answer» A. permeance | |
| 400. |
The property of a material which opposes the creation of magnetic flux in it is known as |
| A. | reluctivity |
| B. | magnetomotive force |
| C. | permeance |
| D. | reluctance |
| Answer» D. reluctance | |
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