Electric Traction MCQ

21. For 600 V dc line for tramcars, track is connected to the

(a) positive of the supply.
(b) negative of the supply.
(c) midvoltage of 300 V.
(d) none of the above.

22. In tramways

(a) the power is supplied at 600 V dc from a single overhead conductor of + ve polarity.
(b) the speed is controlled by field weakening of series parallel control.
(c) rheostatic and mechanical brakings are employed for normal service.
(d) all of the above.

23. The main drawback of tramways is that

(a) the life of tramcar equipment is short.
(b) it has restricted manoeuvrability.
(c) it needs laying overhead supply system and track for its use which is costly to maintain and constitutes a source of danger to other road users.
(d) all of the above.

24. The trolley buses

(a) do not require laying of track for its use as return conductor.
(b) make use of foot operated master controllers.
(c) make use of stabilized rheostatic braking.
(d) all of the above.

25. In diesel electric traction

(a) the driving motors are dc series type and fed from the dc generators driven by the diesel engine put on the same loco-motive.
(b) the starting and speed control is affected by varying the excitation of the generator.
(c) regenerative braking is not possible.
(d) all of the above.

26. Suburban railways use

(a) 1,500 V dc.
(b) 400 V, 3-phase ac.
(c) 3,300 V, 3-phase ac.
(d) 600 V, 3-phase ac.

27. Long distance railways operate on

(a) 600 V dc.
(b) 25 kV single-phase ac.
(c) 25 kV three-phase ac.
(d) 15 kV three-phase ac.

28. The electric locomotives run faster at curved routes in comparison to steam locomotives because

(a) its centre of gravity is lower than that of steam locomotive.
(b) its centre of gravity is higher than that of steam locomotive.
(c) the speed at curved routes is independent of locations of centre of gravity.
(d) none of the above.

29. Low frequency operation of overhead line in traction system

(a) increases the spacing between substations.
(b) reduces the spacing between substations.
(c) spacing is independent of frequency of supply.

30. In Kando system of track electrification

(a) single-phase ac is converted into dc.
(b) single-phase ac is converted into 3-phase ac.
(c) 3-phase ac is converted into dc.
(d) 3-phase ac is converted into single-phase ac.

31. The composite system (single-phase ac to dc system) has been chosen for all future track electrification in India as

(a) it needs light overhead catenary.
(b) it needs less number of substations.
(c) it combines the advantages of high-voltage ac distribution at 50 Hz with dc series traction motors.
(d) it provides flexibility in the location of substations.

32. Single-phase ac system is preferred for main line railway service because

(a) the initial, maintenance and operating costs of ac substations are less as the substation equipment required in single-phase ac system is less, cheap and efficient.
(b) number of substations required is less.
(c) of reduced cost of distribution system.
(d) all of the above.

33. 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

34. 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.

35. 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).

36. 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).

27. The acceleration rate for urban or suburban services is

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

28. The braking retardation for urban or suburban services is

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

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

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

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

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

31. 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.

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

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

33. 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.

34. In suburban services as compared to urban services

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

35. Trapezoidal speed-time curve pertains to

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

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

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

37. Area under the speed-time curve represents

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

38. 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

39. 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.

40. 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.