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
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
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
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
The starting resistance of a D.C. motor is generally_______________?
(A) low
(B) around 500 Q
(C) 1000 Q
(D) infinitely large
Which of the following load normally needs starting torque more than the rated torque?
(A) Blowers
(B) Conveyors
(C) Air compressors
(D) Centrifugal pumps
Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ?
(A) Lenz’s law
(B) Faraday’s law
(C) Coloumb’s law
(D) Fleming’s left-hand rule
In D.C. motor which of the following can sustain the maximum temperature rise?
(A) Slip rings
(B) Commutator
(C) Field winding
(D) Armature winding
The ratio of starting torque to full-load torque is least in case of____________?
(A) series motors
(B) shunt motors
(C) compound motors
(D) none of the above
In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be______________?
(A) 100%
(B) around 90%
(C) anywhere between 75% and 90%
(D) less than 50%