McqMate

55

56.5k

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 |

451. |
## The characteristic impedance of a transmission line with impedance and admittance of 16 and 9 respectively is |

A. | 25 |

B. | 1.33 |

C. | 7 |

D. | 0.75 |

Answer» B. 1.33 |

452. |
## Find the characteristic impedance expression in terms of the inductance and capacitance parameters. |

A. | zo = √(lc) |

B. | zo = lc |

C. | zo = √(l/c) |

D. | zo = l/c |

Answer» C. zo = √(l/c) |

453. |
## When a transmission line has a load impedance same as that of the characteristic impedance, the line is said to be |

A. | parallel |

B. | perpendicular |

C. | polarized |

D. | matched |

Answer» D. matched |

454. |
## The wavelength of a line with a phase constant of 6.28 units is |

A. | 2 |

B. | 1 |

C. | 0.5 |

D. | 3.14 |

Answer» B. 1 |

455. |
## The wavelength of a wave with a frequency of 6 GHz in air is |

A. | 50 |

B. | 5 |

C. | 0.5 |

D. | 0.05 |

Answer» D. 0.05 |

456. |
## The phase constant of a wave with a wavelength of 2 units is given by |

A. | 2 |

B. | 3.14 |

C. | 6.28 |

D. | 1 |

Answer» B. 3.14 |

457. |
## The frequency of a wave travelling in a transmission line with velocity 4 x 108 and wavelength 3 units is |

A. | 0.75 ghz |

B. | 0.133 ghz |

C. | 7.5 ghz |

D. | 1.33 ghz |

Answer» B. 0.133 ghz |

458. |
## The velocity and phase constant relation is given by |

A. | v = ω/β |

B. | v = ωβ |

C. | v = β/ω |

D. | vωβ = 1 |

Answer» A. v = ω/β |

459. |
## The electrical length in a transmission line refers to the |

A. | product of attenuation constant and length |

B. | ratio of attenuation constant and length |

C. | product of phase constant and length |

D. | ratio of phase constant and length |

Answer» A. product of attenuation constant and length |

460. |
## The unit of attenuation constant is |

A. | decibel |

B. | bel |

C. | neper |

D. | no unit |

Answer» C. neper |

461. |
## The propagation constant of a wave with attenuation and phase constant given by 2 and 3 respectively is |

A. | 2 – 3j |

B. | 3 – 2j |

C. | 2 + 3j |

D. | 3 + 2j |

Answer» C. 2 + 3j |

462. |
## The velocity of wave in the air medium is |

A. | 1 x 108 |

B. | 1.5 x 108 |

C. | 3 x 108 |

D. | 1 x 109 |

Answer» C. 3 x 108 |

463. |
## Identify the secondary parameter from the options given below. |

A. | resistance |

B. | conductance |

C. | phase constant |

D. | capacitance |

Answer» C. phase constant |

464. |
## Which of the following parameters does not exist in the transmission line equation? |

A. | r |

B. | zo |

C. | zl |

D. | propagation constant |

Answer» A. r |

465. |
## For an infinite transmission line, the characteristic impedance is given by 50 ohm. Find the input impedance. |

A. | 25 |

B. | 100 |

C. | 2500 |

D. | 50 |

Answer» D. 50 |

466. |
## The best transmission length for effective transmission of power is |

A. | l = λ/4 |

B. | l = λ/8 |

C. | l = λ/2 |

D. | l = ∞ |

Answer» B. l = λ/8 |

467. |
## When the length of the transmission line is same as that of the wavelength, then which condition holds good? |

A. | zin = zo |

B. | z = zo |

C. | zl = zo |

D. | zin = zl |

Answer» D. zin = zl |

468. |
## The input impedance of a half wave transmission line with a load impedance of 12.5 ohm is |

A. | 25 |

B. | 50 |

C. | 6.25 |

D. | 12.5 |

Answer» D. 12.5 |

469. |
## The condition for a quarter wave transformer is |

A. | zo2 = zin zl |

B. | zo = zin zl |

C. | zl2 = zin zo |

D. | zo = zin |

Answer» A. zo2 = zin zl |

470. |
## Find the characteristic impedance of a quarter wave with input and load impedances given by 50 and 25 respectively. |

A. | 50 |

B. | 25 |

C. | 75 |

D. | 35.35 |

Answer» D. 35.35 |

471. |
## Find the load impedance in a quarter line transformer with characteristic impedance of 75 ohm and input impedance of 200 ohm. |

A. | 28.125 |

B. | 12.285 |

C. | 52.185 |

D. | 85.128 |

Answer» A. 28.125 |

472. |
## The reflection coefficient of a perfectly matched transmission line is |

A. | 1 |

B. | -1 |

C. | 0 |

D. | ∞ |

Answer» C. 0 |

473. |
## The purpose of the transmission line equation is to |

A. | find primary parameters |

B. | find secondary parameters |

C. | find the reflection cofficient |

D. | impedance matching |

Answer» D. impedance matching |

474. |
## The quarter wave transformer can be considered as a |

A. | impedance inverter |

B. | impedance doubler |

C. | impedance tripler |

D. | impedance quadrupler |

Answer» A. impedance inverter |

475. |
## Which transmission line is called as one to one transformer? |

A. | l = λ |

B. | l = λ/2 |

C. | l = λ/4 |

D. | l = λ/8 |

Answer» B. l = λ/2 |

476. |
## The characteristic impedance of a quarter wave transformer with load and input impedances given by 30 and 75 respectively is |

A. | 47.43 |

B. | 37.34 |

C. | 73.23 |

D. | 67.45 |

Answer» A. 47.43 |

477. |
## The input impedance of a quarter wave line 50 ohm and load impedance of 20 ohm is |

A. | 50 |

B. | 20 |

C. | 1000 |

D. | 125 |

Answer» D. 125 |

478. |
## The reflection coefficient lies in the range of |

A. | 0 < τ < 1 |

B. | -1 < τ < 1 |

C. | 1 < τ < ∞ |

D. | 0 < τ < ∞ |

Answer» A. 0 < τ < 1 |

479. |
## When the ratio of load voltage to input voltage is 5, the ratio of the characteristic impedance to the input impedance is |

A. | 1/5 |

B. | 5 |

C. | 10 |

D. | 25 |

Answer» B. 5 |

480. |
## The reflection coefficient of a wave with transmission coefficient 0.35 is |

A. | 1.35 |

B. | 0.65 |

C. | 0.35 |

D. | 0.7 |

Answer» B. 0.65 |

481. |
## The incident wave amplitude is 24 units. Find the reflected wave amplitude if the reflection coefficient is 0.6. |

A. | 14.4 |

B. | 16.6 |

C. | 13.3 |

D. | 11.1 |

Answer» A. 14.4 |

482. |
## Find the reflection coefficient of the wave passing through two media having intrinsic impedances of 4 and 9 respectively. |

A. | 0.5 |

B. | 1 |

C. | 0.38 |

D. | 0.1 |

Answer» C. 0.38 |

483. |
## The reflection coefficient of a wave travelling through two media having permittivities 4 and 9 respectively is |

A. | 0 |

B. | 0.5 |

C. | 0.25 |

D. | 0.2 |

Answer» D. 0.2 |

484. |
## Calculate the transmission coefficient, when the incident and transmitted amplitudes are 10 and 7 respectively. |

A. | 17 |

B. | 3 |

C. | 10/7 |

D. | 0.7 |

Answer» D. 0.7 |

485. |
## The transmission coefficient in a wave travelling through two media having intrinsic impedances of 5.5 and 1.33 is |

A. | 0.389 |

B. | 0.55 |

C. | 0.133 |

D. | 0.42 |

Answer» A. 0.389 |

486. |
## The transmission coefficient in a wave travelling through two media having permittivities 4 and 1 is |

A. | 1/4 |

B. | 3/2 |

C. | 3/4 |

D. | 2/3 |

Answer» D. 2/3 |

487. |
## The reflection coefficient of a transmission line having characteristic and load impedances as 50 and 30 ohm respectively is |

A. | 1/4 |

B. | 1/8 |

C. | 1/2 |

D. | 3/4 |

Answer» A. 1/4 |

488. |
## In matched line, the transmission coefficient is |

A. | 0 |

B. | 1 |

C. | -1 |

D. | infinity |

Answer» B. 1 |

489. |
## Standing waves occurs due to |

A. | impedance match |

B. | impedance mismatch |

C. | reflection |

D. | transmission |

Answer» B. impedance mismatch |

490. |
## Standing wave ratio is defined as the |

A. | ratio of voltage maxima to voltage minima |

B. | ratio of current maxima to current minima |

C. | product of voltage maxima and voltage minima |

D. | product of current maxima and current minima |

Answer» A. ratio of voltage maxima to voltage minima |

491. |
## Given that the reflection coefficient is 0.6. Find the SWR. |

A. | 2 |

B. | 4 |

C. | 6 |

D. | 8 |

Answer» B. 4 |

492. |
## The maxima and minima voltage of the standing wave are 6 and 2 respectively. The standing wave ratio is |

A. | 2 |

B. | 3 |

C. | 1/2 |

D. | 4 |

Answer» B. 3 |

493. |
## Find the standing wave ratio, when a load impedance of 250 ohm is connected to a 75 ohm line. |

A. | 0.3 |

B. | 75 |

C. | 250 |

D. | 3.33 |

Answer» D. 3.33 |

494. |
## Find the reflection coefficient of the wave with SWR of 3.5. |

A. | 0.55 |

B. | 0.23 |

C. | 0.48 |

D. | 0.68 |

Answer» A. 0.55 |

495. |
## The range of the standing wave ratio is |

A. | 0 < s < 1 |

B. | -1 < s < 1 |

C. | 1 < s < ∞ |

D. | 0 < s < ∞ |

Answer» C. 1 < s < ∞ |

496. |
## For matched line, the standing wave ratio will be |

A. | 0 |

B. | ∞ |

C. | -1 |

D. | 1 |

Answer» D. 1 |

497. |
## The maximum impedance of a 50 ohm transmission line with SWR of 3 is |

A. | 50/3 |

B. | 3/50 |

C. | 150 |

D. | 450 |

Answer» C. 150 |

498. |
## The minimum impedance of a 75 ohm transmission line with a SWR of 2.5 is |

A. | 100 |

B. | 50 |

C. | 25 |

D. | 30 |

Answer» D. 30 |

499. |
## The standing wave ratio of short circuited and open circuited lines will be |

A. | 0 |

B. | 1 |

C. | -1 |

D. | ∞ |

Answer» D. ∞ |

500. |
## The current reflection coefficient of a line with voltage reflection coefficient of 0.65 is given by |

A. | 0 |

B. | 0.65 |

C. | -0.65 |

D. | 0.35 |

Answer» C. -0.65 |

Done Reading?

Tags

- Question and answers in Electromagnetics,
- Electromagnetics multiple choice questions and answers,
- Electromagnetics Important MCQs,
- Solved MCQs for Electromagnetics,
- Electromagnetics MCQs with answers PDF download