DC MOTORS QUIZ

The iron loss in dc motor depends on

Both flux and speed

Speed only

None of the listed here

Flux only

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Which motor has the poorest speed control?

Differentially compounded motor

Cummulative compounded motor

Shunt motor

Series motor

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______ motors never use belt connected loads.

Cummulative compounded

Shunt

Series

Differentially compounded

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For a D.C. shunt motor if the excitation is changed

Torque will remain constant

Torque and power both will change

Torque will change but power will remain constant

Torque, power and speed, all will change

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A series motor will over speed when

Load is removed

The armature circuit is opened.

The field is opened

The load is increase

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The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is

8.85%

2.22%

6.77%

4.76%

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Which of the following motor is preferred for operation in highly explosive atmosphere?

Air motor

Shunt motor

Battery operated motor

Series motor

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For the same H.P. rating and full load speed, following motor has poor starting torque

Differentially compounded

Cumulatively compounded

Series

Shunt

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Carbon brushes are preferable to copper brushes because _____

They have longer life

They reduce sparking

They have lower resistance

They reduce armature reaction

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

100 %

80 to 90 %

60 to 70 %

Less than 50%

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