DC MOTORS QUIZ

The armature torque of the D.C. shunt motor is proportional to

armature current only

both (A) and (B)

None of these

field flux only

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YOUR ANSWER : ?

When the speed of dc motor increases, its armature current

None of the listed here

Increases

Remains same

Decreases

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Which motor has the poorest speed control?

Series motor

Differentially compounded motor

Shunt motor

Cummulative compounded motor

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D.C. generators are normally designed for maximum efficiency around

All of these

Rated voltage

Rated r.p.m.

Full load

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Which of the following losses are significantly reduced by laminating the core of a D.C. generator?

Copper losses

Eddy current losses

Windage losses

Hysteresis losses

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The shaft torque in a dc motor is less than total armature torque because of ______ in the motor.

Field losses

Iron and friction losses

None of the listed here

Cu losses

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As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit

A resistance is connected parallel to the armature

A resistance is connected in series with armature

Armature is temporarily open circuited

A high value resistor is connected across the field winding

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Which of the following motors is most suitable for signalling devices and many kinds of timers ?

C. series motor

C. shunt motor

Induction motor

Reluctance motor

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If conditions for maximum power for a dc motor are established, the efficiency of the motor will be

60 to 70 %

100 %

Less than 50%

80 to 90 %

TRUE ANSWER : ?
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Armature reaction in dc motor is increased

When the armature current increases

By interpoles

When the armature current decreases

When the field current increases

TRUE ANSWER : ?
YOUR ANSWER : ?

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