1. If the current in the armature of d.c series motor is reduced to 50%, the torque of the motor will become:
(a) 50% of the previous value.
(b) 25% of the previous value.
(c) 150% of the previous value.
(d) 125% of the previous value. [DMRC JE-2016]
Answer: (b) 25% of the previous value.
2. An 8 pole lap wound DC shunt generator is supplying 295A to a load. The field current of the generator is 5A. The current per parallel path is
(a) 300 A
(c) 150 A
(b) 200 A
(d) 37.5 A
Answer: (d) 37.5 A
3. If shunt generator delivers 100 A at 200 V, and the resistance of the shunt field and armature are 100 ohm and 0.01 ohm respectively, the generated e.m.f. will be
(b) 205 V
(a) 212 V
(c) 210 V
(d) 201.02 V
Answer: (d) 201.02 V
4. A 220 V dc shunt motor is running at 500 rpm when armature current is 50 A. The value of armature resistance is 0.2 ohm. The speed of motor at the double torque will be
(a) 250 rpm
(b) 500 rpm
(c) 1000 rpm
(d) 476 rpm [UPPCL JE – 2007]
Answer: (d) 476 rpm
5. A 2 pole generator with wave wound armature has 51 slots each having 24 conductors. The flux per pole is 0.01 wb. The speed at which the generator should run to induce voltage, 220 volt? [UJVNL-2016]
(a) 539 rpm
(b) 750 rpm
(c) 1078 rpm
(d) 1440 rpm
Answer: (c) 1078 rpm
6. A 6 pole Lap wound dc generator has 300 conductors. Emf induced per conductor is 5 volt. This generator will generate emf of
(a) 60 volt
(b) 300 volt
(c) 250 volt
(d) 1800 volt [FCI – 2015]
Answer: (c) 250 volt
7. The induced e.m.f. in the armature of a lap wound 4-pole d.c. machine having 1000 armature conductors rotating at 600 rpm and with 0.1 Wb flux per pole is
(a) 1000 V
(b) 100 V
(c) 10000 V
(d) 10 V [BSNL TTA 2016]
Answer: (a) 1000 V
8. The number of armature parallel paths in a two-pole DC generator having duplex lap winding is
(a) 2
(c) 6
(b) 4
(d) 8 [UPPCL – 2015]
Answer: (b) 4
9. Find the total emf generated in a shunt generator which delivers 200 A at terminal voltage of 230 V, the armature resistance and shunt field resistance are 0.08Ω and 50Ω respectively. [MPJE – 2016]
(a) 246.4 V
(b) 240.6 V
(c) 250.4 V
(d) 260.6 V
Answer: (a) 246.4 V
10. A lap wound DC machine has 400 conductors and 8 poles. The voltage induced per conductor is 2V the machine generates a voltage of
(a) 100 V
(b) 200 V
(c) 400 V
(d) 800 V [UPSSC JE 2016]
Answer: (a) 100 V
11. Given figure is the connection diagram for
(a) Shunt Generator
(b) Series Generator
(c) Shunt or Series Generator
(d) Compound Generator [UPPCL AE 2016]
Answer: (d) Compound Generator
12. The given figure depicts the Torque-Current characteristics of
(a) series motor
(b) shunt motor
(c) cumulative compound motor
(d) differential compound motor [UPPCL JE – 2016]
Answer: (d) differential compound motor
13. A 220 V DC shunt motor runs at 500 rpm when the armature current is 50 A. Now the torque is doubled. What will be the speed if armature resistance is 0.2 Ω ?
(a) 467 rpm
(b) 500 rpm
(c) 476 rpm
(d) 746 rpm
Answer: (c) 476 rpm
14. A 240 V DC series motor takes 40 A when giving its rated output at 1500 rpm. Its resistance is 0.3 ohm. What is the value of resistance which must be added to obtain rated torque at 1000 rpm? [LMRC AE – 2016]
(a) 6 ohms
(b) 5.7 ohms
(c) 2.2 ohms
(d) 1.9 ohms
Answer: (d) 1.9 ohms
15. A 200 V, 2000 rpm, 10 A, separately excited de motor has an armature resistance of 2 ohms, rated DC voltage is applied to both the armature and field winding of the motor. If the armature draws 5A from the source, what is the torque developed by the motor? [LMRC AE 2016]
(a) 4.29 Nm
(b) 5.0 Nm
(c) 5.50 Nm
(d) 6.0 Nm
Answer: (a) 4.29 Nm
16. A 240 V DC shunt motor with an armature resistance of 0.5 ohm has a full load current of 40A. What is the ratio of the stalling torque to the full load torque when a resistance of 1 ohm is connected in series with the armature? [LMRC AE – 2016]
(a) 4
(b) 12
(c) 6
(d) 14
Answer: (a) 4
17. The following figure represents
(a) speed-current characteristics of shunt-motor.
(b) speed-current characteristics of a series motor.
(c) torque-current characteristics of a shunt motor.
(d) torque-current characteristics of a series motor. [ESIC JE – 2016]
Answer: (b) speed-current characteristics of a series motor.
18. The following figure depicts?
(a) Plugging
(b) Regenerative braking
(c) Rheostate Braking
(d) Copper test [UPRVUNL – 2015]
Answer: (c) Rheostate Braking
19. The terminal board of a motor is as shown in the diagram. Which type of motor is this? [MP JE – 2016]
(a) A series motor with commutating pole winding.
(b) A shunt motor with armature winding.
(c) A shunt motor without commutating pole winding.
(d) A series motor with spiral winding.
Answer: (a) A series motor with commutating pole winding.
20. A 230 V DC motor takes a current of 40 A and runs at 1100 r.p.m. If armature and shunt field resistances are 0.25 Ω and 230 Ω respectively the back emf will be
(a) 220.25 V
(b) 110.25 V
(c) 230.25 V
(d) 115 V [LMRC – 2015]
Answer: (a) 220.25 V
21. A 220 V d.c. shunt motor is running at 500 rpm when armature current is 50A. The value of armature resistance is 0.2 ohm. The speed of motor at the double torque will be
(a) 250 rpm
(b) 500 rpm
(c) 1000 rpm
(d) 476 rpm
Answer: (d) 476 rpm
22. A 250 V dc shunt motor has Rf= 125 Ohm and Ra = 0.5 Ohm. The motor operates on no load with full field flux at rated speed of 1000 rpm with If = 5 A. The motor drives a load torque of 100 Nm. Neglecting saturation and armature reaction, the armature current of the motor will be
(a) 40.2 A
(b) 42.2 A
(c) 44.3 A
(d) 46.5 A
Answer: (b) 42.2 A
23. A 240 V, DC series motor draws 30 A when giving its rated output at 1500 rpm. Its armature resistance is 0.3 ohms. The value of resistance that must be inserted in series to obtain rated torque at starting is
(a) 3.3 ohms
(c) 5.5 ohms
(b) 4.5 ohms
(d) 7.7 ohms [UPRVUNL AE – 2016]
Answer: (d) 7.7 ohms
