DC MOTORS QUIZ

The commutating winding is basically used in a dc machine

None of the listed here

To control the speed of machine

To improve commutation

To reduce armature reaction

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By putting controller resistance in series with the armature of a dc motor, we can obtain speeds

Above as well as below the normal speed

Below the normal speed only

None of the listed here

Above the normal speed only

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

Cumulatively compounded

Differentially compounded

Shunt

Series

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The rheostatic speed control method is very

Economical

Efficient

Suitable for getting speeds above the normal

Unsuitable for rapidly changing loads

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For starting a dc motor a starter is required because

It limits the starting current to a safe value

It starts the motor

None of the listed here

It limits the speed of the motor

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The torque developed by a dc motor is directly proportional to

Flux per pole × armature current

None of the listed here

Armature resistance × armature current

Armature resistance × applied voltage

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The maximum end play of a motor is about

0.4 mm

6 mm

2 mm

10 mm

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The dirction of rotation of a dc series motor can be changed by

Either of Interchanging field or Interchanging supply

None of the listed here

Interchanging supply terminals

Interchanging field terminals

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Which method of braking is generally used in elevators?

Plugging

None of these

Rheostat braking

Regenerative braking

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In D.C. shunt motors as load is reduced

The speed will increase in proportion to reduction in load

The speed will reduce

The speed will remain almost/constant

The speed will increase abruptly

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