Electrical Power Engineering Multiple Choice Questions and Answers (MCQs) Part 11:

502. In underground traction, the supply system is

(a) 500 V to 1,000 V dc
(b) 25 kV, 50 Hz
(c) 50 kV, 50 Hz
(d) 25 kV, 25 Hz

Answer : (a) 500 V to 1,000 V dc


503. Problem(s) of single-phase traction systems is/are

(a) current and voltage unbalance.
(b) electrostatic and electromagnetic induction.
(c) generation of harmonics.
(d) all of the above.

Answer : (d) all of the above.


504. The chief requirements of main line railway services are

(a) high maximum speed.
(b) minimum cost of overhead structure.
(c) high acceleration and braking retardation.
(d) both (a) and (b).

Answer : (d) both (a) and (b).


505. The main requirements of suburban railway services are

(a) rapid acceleration and braking retardation.
(b) no interference to the communication circuits running along the track.
(c) high maximum speed.
(d) both (a) and (b).

Answer : (d) both (a) and (b).


506. The acceleration rate for urban or suburban services is

(a) 1.5-4 kmphps.
(b) 3-4 kmphps.
(c) 5-10 kmphps.
(d) 0.5-1.5 kmphps.

Answer : (a) 1.5-4 kmphps.


507. The braking retardation for urban or suburban services is

(a) 1.5-2.5 kmphps.
(b) 3-4 kmphps.
(c) 5-10 kmphps.
(d) 0.5-1.5 kmphps.

Answer : (b) 3-4 kmphps.


508. The coasting retardation for main line railway services is about

(a) 10 kmphps.
(b) 3 kmphps.
(c) 0.16 kmphps.
(d) 0.01 kmphps.

Answer : (c) 0.16 kmphps.


509. The maximum speed at which trains run on main line railway service is

(a) 160 kmph.
(b) 120 kmph.
(c) 100 kmph.
(d) 200 kmph.

Answer : (a) 160 kmph.


510. In main line services as compared to urban and suburban services

(a) distance between the stops is more (exceeding 10 km).
(b) maximum speed attained is high.
(c) acceleration and braking retardation rates are low.
(d) all of the above.

Answer : (d) all of the above.


511. The speed-time curve for urban service has no

(a) coasting period.
(b) free running period.
(c) braking period.
(d) acceleration period.

Answer : (b) free running period.


512. Free running and coasting periods are generally long in case of

(a) city service.
(b) suburban service.
(c) main line service.
(d) outer suburban service.

Answer : (c) main line service.


513. In suburban services as compared to urban services

(a) the coasting period is longer.
(b) the coasting period is smaller but free miming period is longer.
(c) the coasting and free running periods are smaller.
(d) none of the above is true.

Answer : (a) the coasting period is longer.


514. Trapezoidal speed-time curve pertains to

(a) main line service.
(b) urban service.
(c) suburban service.
(d) urban/suburban service.

Answer : (a) main line service.


515. Quadrilateral speed-time curve is the close approximation for

(a) urban service.
(b) suburban service.
(c) urban/suburban service.
(d) main line service.

Answer : (c) urban/suburban service.


516. The speed-time curve for a main line service is illustrated in figure given below.

In figure given below AB represents

Speed-time curve

(a) coasting.
(b) free running.
(c) acceleration.
(d) average speed.

Answer : (b) free running.


517. Area under the speed-time curve represents

(a) total distance travelled.
(b) average speed.
(c) average acceleration.
(d) none of the above.

Answer : (a) total distance travelled.


518. The duration of coasting is represented by the duration

(a) 0 – t1
(b) t1 – t2
(c) t2 – t3
(d) t3 – t4

Answer : (c) t2 – t3


519. From figure given in Q. 516, it can be concluded that

(a) average acceleration is zero.
(b) during coasting and braking the acceleration is negative.
(c) acceleration during free running is zero.
(d) both (b) and (c).

Answer : (d) both (b) and (c).


520. The speed of train estimated taking into account the stoppage time at a station in addition to the actual running time between stops, is called the ……….. speed.

(a) average
(b) schedule
(c) free running
(d) notching

Answer : (b) schedule


521. The average speed of a train is independent of

(a) duration of stops.
(b) acceleration and braking retardation.
(c) distance between stops.
(d) running time.

Answer : (a) duration of stops.


522. The schedule speed of a given train when running on a given service (with given distance between stations) is affected by

(a) acceleration and braking retardation.
(b) maximum or crest speed.
(c) duration of stop.
(d) all of the above.

Answer : (d) all of the above.


523. Skidding of a vehicle always occurs when

(a) braking effort exceeds its adhesive weight.
(b) brake is applied suddenly.
(c) it negotiates a curve.
(d) it passes over points and crossings.

Answer : (a) braking effort exceeds its adhesive weight.


524. The adhesive weight is the

(a) total weight of the locomotive and the train.
(b) weight coming over the driving wheels.
(c) same as the accelerating weight.
(d) none of the above.

Answer : (b) weight coming over the driving wheels.


525. Coefficient of adhesion is the ratio of tractive effort to slip the wheels and

(a) dead weight.
(b) accelerating weight.
(c) adhesive weight.
(d) none of the above.

Answer : (c) adhesive weight.


526. The normal value of coefficient of adhesion is

(a) 0.25
(b) 0.35
(c) 0.50
(d) 0.65

Answer : (a) 0.25


527. Coefficient of adhesion reduces due to the presence of

(a) dew on rails.
(b) oil and grease on rails.
(c) dry sand on rails.
(d) both (a) and (b).

Answer : (d) both (a) and (b).


528. Coefficient of adhesion improves due to presence of

(a) dry sand on rails.
(b) rust on rails.
(c) dust on rails.
(d) all of the above.

Answer : (d) all of the above.


529. The value of coefficient of adhesion will be high when rails are

(a) wet.
(b) cleaned with sand.
(c) greased.
(d) sprayed with oil.

Answer : (b) cleaned with sand.


530. The coefficient of adhesion for wet or greasy rails is

(a) 0.35
(b) 0.25
(c) 0.08
(d) zero

Answer : (c) 0.08


531. The coefficient of adhesion

(a) same on dc and ac traction.
(b) high in ac traction and low in dc traction.
(c) high in dc traction and low in ac traction.
(d) any of the above.

Answer : (b) high in ac traction and low in dc traction.


532. Higher value of tractive effort can be used in electric traction as compared to steam traction because

(a) of greater adhesive weight (the weight on driving wheels is 70 percent of dead weight in case of electric locomotive whereas in case of steam locomotive it is 50 percent).
(b) the torque exerted in electric traction is continuous whereas in steam traction it is pulsating one.
(c) the driving wheels are distributed over a much greater length in electric traction whereas in steam traction they are close to each other.
(d) all of the above.

Answer : (d) all of the above.


533. When a bogie negotiates a curve, reduction in adhesion occurs resulting in sliding. This sliding is acute when

(a) degree of curvature is more.
(b) wheel base of axles is more.
(c) none of the above.
(d) both (a) and (b).

Answer : (d) both (a) and (b).


534. For a given maximum axle load tractive effort with ac locomotive will be

(a) less than that of dc locomotive.
(b) more than that of dc locomotive.
(c) equal to that of dc locomotive.
(d) none of the above.

Answer : (b) more than that of dc locomotive.


535. The resistance encountered by a train in motion is on account of

(a) resistance offered by air.
(b) friction at the track.
(c) friction at various parts of the rolling stock.
(d) all of the above.

Answer : (d) all of the above.


536. The air resistance to the movement of the train is proportional to

(a) 1/speed.
(b) (speed).
(c) (speed)2.
(d) (speed)3.

Answer : (c) (speed)2.


537. The friction at the track is proportional to

(a) speed.
(b) (speed)2.
(c) (speed)3.
(d) (1/speed)2.

Answer : (a) speed.


538. If the resistance to electric train movement is given by

Fr = a + bv + cv2

In the above expression b is likely to cover

(a) air resistance.
(b) track resistance.
(c) frictional resistance.
(d) none of the above.

Answer : (b) track resistance.


539. Tractive effort of an electric locomotive can be increased by

(a) using high output motors.
(b) increasing the supply voltage.
(c) increasing dead weight over the driving axles.
(d) both (a) and (c).

Answer : (d) both (a) and (c).


540. A locomotive with a mass of 50,000 kg on a track whose coefficient of adhesion is 20 per cent will produce a tractive effort of (approximately)

(a) 1 kN
(b) 100 kN
(c) 25 kN
(d) 250 kN

Answer : (b) 100 kN


541. Energy consumption in propelling the train is required for

(a) accelerating of train mass.
(b) overcoming the gradient while moving up the gradient.
(c) overcoming the train resistance.
(d) all of the above.

Answer : (d) all of the above.


542. Longer coasting period for a train results in

(a) higher schedule speed.
(b) lower specific energy consumption.
(c) higher retardation.
(d) higher acceleration.

Answer : (b) lower specific energy consumption.


543. Specific energy consumption is affected by

(a) acceleration and retardation values.
(b) the crest speed and nature of route.
(c) distance between stops.
(d) all of the above.

Answer : (d) all of the above.


544. Specific energy consumption is minimum in ………… services.

(a) main line
(b) urban
(c) suburban
(d) equal for all type of

Answer : (a) main line


545. For a given run and given schedule speed, the specific energy consumption is

(a) lower, the higher the acceleration and retardation.
(b) higher, the higher the acceleration and retardation.
(c) lower, the higher the acceleration and lower the retardation.
(d) lower, the lower the acceleration and higher the retardation.

Answer : (a) lower, the higher the acceleration and retardation.


546. Specific energy consumption

(a) increases with the increase in maximum speed.
(b) decreases with the increase in maximum speed.
(c) is independent of maximum speed.
(d) none of the above.

Answer : (a) increases with the increase in maximum speed.


547. If the speed-time curves are similar (not identical), the specific energy consumption of the curve having higher maximum speed is ………. than that of lower maximum speed.

(a) lower
(b) equal
(c) higher
(d) none

Answer : (b) equal


548. Specific energy consumption becomes

(a) more when distance between stops is more.
(b) more with the higher values of acceleration (or retardation).
(c) more with high train resistance.
(d) less with the increase in crest speed.

Answer : (c) more with high train resistance.


549. The specific energy consumption for suburban services is usually ………… watt-hours per tonne-km.

(a) 20-30
(b) 30-45
(c) 50-75
(d) 100-150

Answer : (c) 50-75


550. The specific energy consumption for main line services is around ………. watt hours per tonne-km.

(a) 20-30
(b) 30-45
(c) 50-75
(d) 100-150

Answer : (a) 20-30


551. Specific energy consumption is maximum in ………. services.

(a) urban
(b) suburban
(c) main line
(d) equal for all types of

Answer : (a) urban

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