(a) It limits the speed of the motor
(b) It limits the starting current to a safe value
(c) It starts the motor
(d) None of the above
Ans. (b) It limits the starting current to a safe value
Q.2. The type of D.C. motor used for shears and punches is
(a) Shunt motor
(b) Series motor
(c) Differential compound D.C. motor
(d) Cumulative compound D.C. motor
Ans. (d) Cumulative compound D.C. motor
Q.3. If a D.C. motor is connected across the A.C. supply it will
(a) Run at normal speed
(b) Not run
(c) Run at lower speed
(d) Burn due to heat produced in the field winding by eddy currents
Ans. (d) Burn due to heat produced in the field winding by eddy currents
Q.4. To get the speed of D.C. motor below the normal without wastage of electrical energy is used.
(a) Ward Leonard control
(b) Rheostatic control
(c) Any of the above method
(d) None of the above method
Ans. (a) Ward Leonard control
Q.5. When two D.C. series motors are connected in parallel, the resultant speed is
(a) More than the normal speed
(b) Loss than the normal speed
(c) Normal speed
(d) Zero
Ans. (c) Normal speed
Q.6. The speed of a D.C. shunt motor more than its full-load speed can be obtained by
(a) Decreasing the field current
(b) Increasing the field current
(c) decreasing the armature current
(d) Increasing the armature current
Ans. (a) Decreasing the field current
Q.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
Ans. (a) Independent of armature current
Q.8. A direct on line starter is used for starting motors
(a) Up to 5 H.P.
(b) Up to 10 H.P.
(c) Up to 15 H.P.
(d) Up to 20 H.P.
Ans. (a) Up to 5 H.P.
Q.9. What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
(a) The motor will stop
(b) The motor will continue to run
(c) The armature may burn
(d) The motor will run noisy
Ans. (c) The armature may burn
Q.10. In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
(a) Back e.m.f. is equal to armature drop
(b) Armature drop is negligible
(c) Flux is proportional to armature current
(d) Flux is practically constant in D.C. shunt motors
Ans. (d) Flux is practically constant in D.C. shunt motors
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