In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be

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

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

A

field flux only

B

armature current only

C

both (A) and (B)

D

none of the above

A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will

A

remain same

B

go down

C

improve

D

none of the above

As the load is applied to a synchronous motor, the motor takes more armature current because

A

The increased load has to take more current

B

The rotor by shifting its phase backward causes motor to take more current

C

The back e.m.f. decreases causing an increase in motor current

D

The rotor strengthens the rotating field causing more motor current

When load on an over-excited or under excited synchronous motor is increased, rate of change of its armature current as compared with that of power factor is

A

more

B

less

C

equal

D

twice

The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is

A

4.0

B

2.0

C

1.0

D

0.5

In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be

A

100%

B

Around 90%

C

Anywhere between 75% and 90%

D

Less than 50%

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

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 reduce

C

The motor will attain dangerously high speed 1

D

The motor will continue to run at constant speed

In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be

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