MULTIPLE CHOICE QUESTIONS
Q.1 The output power of any electrical motor is taken from the:
(A) armature
(B) field
(C) coupling mounted on the shaft
(D) motor frame
Q.2 If the back emf in a dc motor varnishes suddenly, then the motor:
(A) run at very high speeds
(B) start hunting
(C) burn
(D) come to stall
Q.3 The direction of the armature current in a dc motor is:
(A) the same as the generated emf
(B) opposite to that of generated emf
(C) not dependent upon the direction of the armature emf
(D) none of the above
Q.4 When a dc machine is connected to the dc supply main it will
produce:
(A) emf in opposition to the applied voltage
(B) emf in phase with the applied voltage
(C) emf decreases with time
(D) none of the above
Q.5 The direction of rotation of a dc motor can be determined by:
(A) fleming's right hand rule
(B) fleming's left hand rule
(C) lenz's law
(D) ampere's law
Q.6 A thick wire is used in dc series motor field winding than that
in dc shunt motor:
(A) to create more flux
(B) to reduce the resistance
(C) to carry large load current
(D) both (b) and (c)
Q.7 An electrical train employing a dc series motor is running at the fixed speed, when a sudden slight drop in the mains voltage occurs. This would result in:
(A) drop in the speed and rise in the current
(B) rise in the speed and drop in the current
(C) rise in the speed and rise in the current
(D) drop in speed with current unaltered
Q.8 A DC shunt motor is driving a constant torque load. On inserting
an additional resistance in the armature circuit, the speed of the motor will:
(A) remains unchanged
(B) increases
(C) decreases
(D) be Zero
Q.9 A DC series motor is best suited for electrical traction
because:
(A) it develops high starting torque
(B) it runs at very high speed
(C) it is cheaper in cost
(D) it is more rugged in construction like induction motor
Q.10. A DC series motor is used for overhauling load. It can work
stable if:
(A) the armature is shunted by a resistor
(B) the field winding is revered
(C) a resistor is put in series with the machine
(D) a divertor is put across the field.
