In case of D.C. shunt motors the speed is dependent on back e.m.f. only because

If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens

A

This will make armature to take heavy current, possibly burning it

B

This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses

C

Nothing will happen to motor

D

Motor will come to stop

If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens

A

Nothing will happen to the motor

B

This will make armature to take heavy current, possibly burning it

C

This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses

D

Motor will run at very slow speed

D.C. shunt motors are used for driving

A

Trains

B

Cranes

C

Hoists

D

Machine tools

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

Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?

A

Low cost

B

Wide speed range

C

Stability

D

High starting torque

A person goes from point N to P and comes back. His average speed for the whole journey is 60 km/hr. If his speed while going from N to P is 40 km/hr, then what will be the speed of the person (in km/hr) while coming back from P to N?

A

80

B

100

C

120

D

140

If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will

A

Increase

B

Decrease

C

Remain same

D

Become zero

A delivery car went from Candleford to Lark Rise and back at an average speed of23 miles per hour. If the distance from Candleford to Lark Rise is 1 mile, and the trip back too half as much time as the trip there, what was the average speed of the delivery car on the way to Lark Rise?

A

13

B

34

C

12

D

23

A delivery cart went from Candle ford to Lark Rise and back at an average speed of 2/3 miles per hour. If the distance from Candle ford to Lark Rise is 1 mile, and the trip back took half as much time as the trip there, what was the average speed of the delivery cart on the way to Lark Rise?

A

1/3

B

3/4

C

1/2

D

2/3

The speed of a DC shunt motor is required to be more than full load speed . This is possible by-

A

reducing the field current

B

decreasing the armature current

C

increasing the armature current

D

None of the above

In case of D.C. shunt motors the speed is dependent on back e.m.f. only because

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