D.C. Motors

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 type of D.C. motor used for shears and punches is_____________?

A. shunt motor
B. series motor
C. differential compoutid D.C. motor
D. cumulative compound D.C. motor

For starting a D.C. motor a starter is required because___________?

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

A D.C. series motor is that which______________?

A. has its field winding consisting of thick wire and less turns
B. has a poor torque
C. can be started easily without load
D. has almost constant speed

In D.C. shunt motors as load is reduced__________________?

A. the speed will increase abruptly
B. the speed will increase in proportion to reduction in load
C. the speed will remain almost/constant
D. the speed will reduce

Starters are used with D.C. motors because______________?

A. these motors have high starting torque
B. these motors are not self-starting
C. back e.m.f. of these motors is zero initially
D. to restrict armature current as there is no back e.m.f. while starting

If the field of a D.C. shunt motor gets opened while motor is running______________?

A. the speed of motor will be reduced %
B. the armature current will reduce
C. the motor will attain dangerously high speed 1
D. the motor will continue to nuvat constant speed