July 2018

If I2 be the armature current, then speed of a D.C. shunt motor is_______________?

A. independent of Ia
B. proportional to la
C. varies as (Ia)
D. varies as la

The speed of a D.C. shunt motor can be increased by_______________?

A. increasing the resistance in armature circuit
B. increasing the resistance in field circuit
C. reducing the resistance in the field circuit
D. reducing the resistance in the armature circuit

As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit____________________?

A. a resistance is connected in series with armature
B. a resistance is connected parallel to the armature
C. armature is temporarily open circuited
D. a high value resistor is connected across the field winding

The armature voltage control of D.C. motor provides____________?

A. constant torque drive
B. constant voltage drive
C. constant current drive
D. none of the above

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______________?

A. 2.36%
B. 4.76%
C. 6.77%
D. 8.84%

Usually wide and sensitive speed control is desired in case of____________?

A. centrifugal pumps
B. elevators
C. steel rolling mills
D. colliery winders

Which of the following method of speed control of D.C. machine will offer minimum efficiency ?

A. Voltage control method
B. Field control method
C. Armature control method
D. All above methods

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

As -the load is increased the speed of D.C. shunt motor will____________?

A. reduce slightly
B. increase slightly
C. increase proportionately
D. remains unchanged