Electrical Studys

1➤ No-load speed of which of the following motor will be highest ?

A. Shunt motorB. Series motorC. Cumulative compound motorD. Differentiate compound motor

2➤ The direction of rotation of a D.C. series motor can be changed by

A. interchanging supply terminalsB. interchanging field terminalsC. either of (a) and (b) aboveD. None of the above

3➤ Which of the following application requires high starting torque ?

A. Lathe machineB. Centrifugal pumpC. LocomotiveD. Air blower

4➤ If a D.C. motor is to be selected for conveyors, which motor would be preferred ?

A. Series motorB. Shunt motorC. Differentially compound motorD. Cumulative compound motor

5➤ Which D.C. motor will be preferred for machine tools ?

A. Series motorB. Shunt motorC. Cumulative compound motorD. Differential compound motor

6➤ Differentially compound D.C. motors can find applications requiring

A. high starting torqueB. low starting torqueC. variable speedD. frequent on-off cycles

7➤ Which D.C. motor is preferred for elevators ?

A. Shunt motorB. Series motorC. Differential compound motorD. Cumulative compound motor

8➤ 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 reduceC. the motor will attain dangerously high speed 1D. the motor will continue to nuvat constant speed

9➤ Starters are used with D.C. motors because

A. these motors have high starting torqueB. these motors are not self-startingC. back e.m.f. of these motors is zero initiallyD. to restrict armature current as there is no back e.m.f. while starting

10➤ In D.C. shunt motors as load is reduced

A. the speed will increase abruptlyB. the speed will increase in proportion to reduction in loadC. the speed will remain almost/constantD. the speed will reduce

11➤ A D.C. series motor is that which

A. has its field winding consisting of thick wire and less turnsB. has a poor torqueC. can be started easily without loadD. has almost constant speed

12➤ For starting a D.C. motor a starter is required because

A. it limits the speed of the motorB. it limits the starting current to a safe valueC. it starts the motorD. none of the above

13➤ The type of D.C. motor used for shears and punches is

A. shunt motorB. series motorC. differential compoutid D.C. motorD. cumulative compound D.C. motor

14➤ If a D.C. motor is connected across the A.C. supply it will

A. run at normal speedB. not runC. run at lower speedD. burn due to heat produced in the field winding by eddy currents

15➤ To get the speed of D.C, motor below the normal without wastage of electrical energy is used.

A. Ward Leonard controlB. rheostatic controlC. any of the above methodD. None of the above method

16➤ When two D.C. series motors are connected in parallel, the resultant speed is

A. more than the normal speedB. loss than the normal speedC. normal speedD. zero

17➤ The speed of a D.C. shunt motor more than its full-load speed can be obtained by

A. decreasing the field currentB. increasing the field currentC. decreasing the armature currentD. increasing the armature current

18➤ In a D.C. shunt motor, speed is

A. independent of armature currentB. directly proportional to the armature currentC. proportional to the square of the currentD. inversely proportional to the armature current

19➤ A direct on line starter is used for starting motors

A. Up to 5 H.PB. Up to 10 H.PC. Up to 15 H.PD. Up to 20 H.P

20➤ What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?

A. The motor will stopB. The motor will continue to runC. The armature may burnD. The motor will run noisy

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