# Practice Test: Question Set - 08

1. Differentially compound D.C. motors can find applications requiring
(A) High starting torque
(B) Low starting torque
(C) Variable speed
(D) Frequent on-off cycles

2. In D.C. machines the residual magnetism is of the order of
(A) 2 to 3 percent
(B) 10 to 15 percent
(C) 20 to 25 percent
(D) 50 to 75 percent

3. Usually wide and sensitive speed control is desired in case of
(A) Centrifugal pumps
(B) Elevators
(C) Steel rolling mills
(D) Colliery winders

4. Which of the following motors one will choose to drive the rotary compressor?
(A) D.C. shunt motor
(B) D.C. series motor
(C) Universal motor
(D) Synchronous motor

5. The total losses in a well designed D.C. generator of 10 kW will be nearly
(A) 100 W
(B) 500 W
(C) 1000 W
(D) 1500 W

6. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens
(A) This will make armature to take heavy current, possibly burning it
(B) This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
(C) Nothing will happen to motor
(D) Motor will come to stop

7. In a D.C. shunt motor, speed is
(A) Independent of armature current
(B) Directly proportional to the armature current
(C) Proportional to the square of the current
(D) Inversely proportional to the armature current

8. Which of the following law/rule can he used to determine the direction of rotation of D.C. motor?
(A) Lenz's law
(C) Coulomb’s law
(D) Fleming's left-hand rule

9. Which of the following motor is preferred for operation in highly explosive atmosphere?
(A) Series motor
(B) Shunt motor
(C) Air motor
(D) Battery operated motor

10. The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is
(A) 2.36%
(B) 4.76%
(C) 6.77%
(D) 8.84%

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