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

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

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 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

If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor

A

will become more

B

will become less

C

will remain unchanged

D

none of the above.

If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor

A

become more

B

become less

C

remain constant

D

none of the above

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

A

Almost negligible

B

Rated full-load current

C

Less than full-load current

D

More than full-load current

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 case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will

A

Remain unchanged

B

Reduce to one-fourth value

C

Increase four folds

D

Be doubled

In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then

A

the motor is said to be fully loaded

B

the torque generated is maximum

C

the excitation is said to be zero per cent

D

the excitation is said to be hundred per cent

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

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