McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 401. |
The unit of retentivity is |
| A. | weber |
| B. | weber/sq. m |
| C. | ampere turn/metre |
| D. | ampere turn |
| Answer» B. weber/sq. m | |
| 402. |
Reciprocal of reluctance is |
| A. | reluctivity |
| B. | permeance |
| C. | permeability |
| D. | susceptibility |
| Answer» B. permeance | |
| 403. |
The unit of reluctance is |
| A. | metre/henry |
| B. | henry/metre |
| C. | henry |
| D. | 1/henry |
| Answer» D. 1/henry | |
| 404. |
A ferrite core has less eddy current loss than an iron core because |
| A. | ferrites have high resistance |
| B. | ferrites are magnetic |
| C. | ferrites have low permeability |
| D. | ferrites have high hysteresis |
| Answer» D. ferrites have high hysteresis | |
| 405. |
Hysteresis loss least depends on |
| A. | volume of material |
| B. | frequency |
| C. | steinmetz co-efficient of material |
| D. | ambient temperature |
| Answer» D. ambient temperature | |
| 406. |
Laminated cores, in electrical machines, are used to reduce |
| A. | copper loss |
| B. | eddy current loss |
| C. | hysteresis loss |
| D. | all of the above |
| Answer» B. eddy current loss | |
| 407. |
The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as |
| A. | self-inductance |
| B. | mutual inductance |
| C. | series aiding inductance |
| D. | capacitance |
| Answer» A. self-inductance | |
| 408. |
Which of the following circuit element stores energy in the electromagnetic field ? |
| A. | inductance |
| B. | condenser |
| C. | variable resistor |
| D. | resistance |
| Answer» A. inductance | |
| 409. |
Higher the self-inductance of a coil, |
| A. | lesser its weber-turns |
| B. | lower the e.m.f. induced |
| C. | greater the flux produced by it |
| D. | longer the delay in establishing steady current through it |
| Answer» D. longer the delay in establishing steady current through it | |
| 410. |
In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will |
| A. | increase |
| B. | decrease |
| C. | remain the same |
| D. | initially increase and then decrease |
| Answer» B. decrease | |
| 411. |
Both the number of turns and the core length of an inductive coil are doubled. Its self-inductance will be |
| A. | unaffected |
| B. | doubled |
| C. | halved |
| D. | quadrupled |
| Answer» B. doubled | |
| 412. |
If current in a conductor increases then according to Lenz's law self-induced voltage will |
| A. | aid the increasing current |
| B. | tend to decrease the amount of cur-rent |
| C. | produce current opposite to the in-creasing current |
| D. | aid the applied voltage |
| Answer» C. produce current opposite to the in-creasing current | |
| 413. |
The direction of incViced e.m.f. can be found by |
| A. | laplace\s law |
| B. | lenz\s law |
| C. | fleming\s right hand rule |
| D. | kirchhoff s voltage law |
| Answer» B. lenz\s law | |
| 414. |
Air-core coils are practically free from |
| A. | hysteresis losses |
| B. | eddy current losses |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» C. both (a) and (b) | |
| 415. |
The magnitude of the induced e.m.f. in a conductor depends on the |
| A. | flux density of the magnetic field |
| B. | amount of flux cut |
| C. | amount of flux linkages |
| D. | rate of change of flux-linkages |
| Answer» D. rate of change of flux-linkages | |
| 416. |
Mutually inductance between two magnetically-coupled coils depends on |
| A. | permeability of the core |
| B. | the number of their turns |
| C. | cross-sectional area of their com-mon core |
| D. | all of the above |
| Answer» D. all of the above | |
| 417. |
A laminated iron core has reduced eddy-current losses because |
| A. | more wire can be used with less d.c. resistance in coil |
| B. | the laminations are insulated from each other |
| C. | the magnetic flux is concentrated in the air gap of the core |
| D. | the laminations are stacked vertf-cally |
| Answer» B. the laminations are insulated from each other | |
| 418. |
The law that the induced e.m.f. and current always oppose the cause producing them is due to |
| A. | faraday |
| B. | lenz |
| C. | newton |
| D. | coulomb |
| Answer» B. lenz | |
| 419. |
Which of the following is not a unit of inductance ? |
| A. | henry |
| B. | coulomb/volt ampere |
| C. | volt second per ampere |
| D. | all of the above |
| Answer» B. coulomb/volt ampere | |
| 420. |
In case of an inductance, current is proportional to |
| A. | voltage across the inductance |
| B. | magnetic field |
| C. | both (a) and (b) |
| D. | neither (a) nor (b) |
| Answer» B. magnetic field | |
| 421. |
Which of the following circuit elements will oppose the change in circuit current ? |
| A. | capacitance |
| B. | inductance |
| C. | resistance |
| D. | all of the above |
| Answer» B. inductance | |
| 422. |
For a purely inductive circuit which of the following is true ? |
| A. | apparent power is zero |
| B. | relative power is.zero |
| C. | actual power of the circuit is zero |
| D. | any capacitance even if present in the circuit will not be charged |
| Answer» C. actual power of the circuit is zero | |
| 423. |
Which of the following is unit of inductance ? |
| A. | ohm |
| B. | henry |
| C. | ampere turns |
| D. | webers/metre |
| Answer» B. henry | |
| 424. |
An e.m.f. of 16 volts is induced in a coil of inductance 4H. The rate of change of current must be |
| A. | 64 a/s |
| B. | 32 a/s |
| C. | 16 a/s |
| D. | 4 a/s |
| Answer» D. 4 a/s | |
| 425. |
The self inductances of two coils are 8 mH and 18 mH. If the co-efficients of coupling is 0.5, the mutual inductance of the coils is |
| A. | 4 mh |
| B. | 5 mh |
| C. | 6 mh |
| D. | 12 mh |
| Answer» C. 6 mh | |
| 426. |
Two coils have inductances of 8 mH and 18 mH and a co-efficient of coupling of 0.5. If the two coils are connected in series aiding, the total inductance will be |
| A. | 32 mh |
| B. | 38 mh |
| C. | 40 mh |
| D. | 48 mh |
| Answer» B. 38 mh | |
| 427. |
A 200 turn coil has an inductance of 12 mH. If the number of turns is increased to 400 turns, all other quantities (area, length etc.) remaining the same, the inductance will be |
| A. | 6 mh |
| B. | 14 mh |
| C. | 24 mh |
| D. | 48 mh |
| Answer» D. 48 mh | |
| 428. |
Two coils have self-inductances of 10 H and 2 H, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be |
| A. | 6 h |
| B. | 8 h |
| C. | 12 h |
| D. | 24 h |
| Answer» C. 12 h | |
| 429. |
In case all the flux from the current in coil 1 links with coil 2, the co-efficient of coupling will be |
| A. | 2.0 |
| B. | 1.0 |
| C. | 0.5 |
| D. | zero |
| Answer» B. 1.0 | |
| 430. |
A coil with negligible resistance has 50V across it with 10 mA. The inductive reactance is |
| A. | 50 ohms |
| B. | 500 ohms |
| C. | 1000 ohms |
| D. | 5000 ohms |
| Answer» D. 5000 ohms | |
| 431. |
Lenz's law is a consequence of the law of conservation of |
| A. | induced current |
| B. | charge |
| C. | energy |
| D. | induced e.m.f. |
| Answer» C. energy | |
| 432. |
A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla. The force on the conductor will be nearly |
| A. | 50 n |
| B. | 120 n |
| C. | 240 n |
| D. | 480 n |
| Answer» B. 120 n | |
| 433. |
Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla. |
| A. | 100 n |
| B. | 400 n |
| C. | 600 n |
| D. | 1000 n |
| Answer» A. 100 n | |
| 434. |
The co-efficient of coupling between two air core coils depends on |
| A. | self-inductance of two coils only |
| B. | mutual inductance between two coils only |
| C. | mutual inductance and self inductance of two coils |
| D. | none of the above |
| Answer» C. mutual inductance and self inductance of two coils | |
| 435. |
An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is |
| A. | 20 wb |
| B. | 2 wb |
| C. | 0.2 wb |
| D. | 0.02 wb |
| Answer» D. 0.02 wb | |
| 436. |
A 500 turns solenoid develops an average induced voltage of 60 V. Over what time interval must a flux change of 0.06 Wb occur to produce such a voltage ? |
| A. | 0.01 s |
| B. | 0.1 s |
| C. | 0.5 s |
| D. | 5 s |
| Answer» C. 0.5 s | |
| 437. |
Which of the fpllowing inductor will have the least eddy current losses ? |
| A. | air core |
| B. | laminated iron core |
| C. | iron core |
| D. | powdered iron core |
| Answer» A. air core | |
| 438. |
A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of inductance is |
| A. | 3500 mh |
| B. | 350 mh |
| C. | 250 mh |
| D. | 150 mh |
| Answer» B. 350 mh | |
| 439. |
Two 300 uH coils in series without mutual coupling have a total inductance of |
| A. | 300 uh |
| B. | 600 uh |
| C. | 150 uh |
| D. | 75 uh |
| Answer» B. 600 uh | |
| 440. |
Current changing from 8 A to 12 A in one second induced 20 volts in a coil. The value of inductance is |
| A. | 5 mh |
| B. | 10 mh |
| C. | 5 h |
| D. | 10 h |
| Answer» C. 5 h | |
| 441. |
Which circuit element(s) will oppose the change in circuit current ? |
| A. | resistance only |
| B. | inductance only |
| C. | capacitance only |
| D. | inductance and capacitance |
| Answer» B. inductance only | |
| 442. |
A crack in the magnetic path of an inductor will result in |
| A. | unchanged inductance |
| B. | increased inductance |
| C. | zero inductance |
| D. | reduced inductance |
| Answer» D. reduced inductance | |
| 443. |
A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by |
| A. | variation in coil current |
| B. | variation in voltage to the coil |
| C. | change of number of turns of coil |
| D. | the resistance of magnetic path |
| Answer» B. variation in voltage to the coil | |
| 444. |
Which of the following parameters is not a primary parameter? |
| A. | resistance |
| B. | attenuation constant |
| C. | capacitance |
| D. | conductance |
| Answer» B. attenuation constant | |
| 445. |
The networks in which the R, L, C parameters are individually concentrated or lumped at discrete points in the circuit are called |
| A. | lumped |
| B. | distributed |
| C. | parallel |
| D. | paired |
| Answer» A. lumped | |
| 446. |
The lines having R, L, C distributed along the circuit are called |
| A. | lumped |
| B. | distributed |
| C. | parallel |
| D. | paired |
| Answer» B. distributed | |
| 447. |
Which primary parameter is uniformly distributed along the length of the conductor? |
| A. | g |
| B. | c |
| C. | l |
| D. | r |
| Answer» D. r | |
| 448. |
The primary parameter that is associated with the magnetic flux linkage is |
| A. | r |
| B. | l |
| C. | c |
| D. | g |
| Answer» B. l | |
| 449. |
The primary parameter that is associated with the electric charges is |
| A. | g |
| B. | r |
| C. | c |
| D. | l |
| Answer» C. c | |
| 450. |
Find the receiving impedance of a transmission line having a voltage of 24V and a conduction current of 1.2A is |
| A. | 25.2 |
| B. | 22.8 |
| C. | 28.8 |
| D. | 20 |
| Answer» D. 20 | |
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