Page 663 - Basic Electrical Engineering

d. EMF induced is inversely proportional to the number of poles.

3. The poles and armature of a dc machine is made of laminated steel sheets to

a. reduce hysteresis loss
b. reduced eddy current loss
2
c. reduce I R loss
d. reduce humming noise of the core.

4. The EMF induced in the armature of a dc generator is alternating in nature but in the output
circuit dc is made available by

a. Brush and slip-ring arrangement
b. Brush and commutator arrangement
c. diode rectifiers
d. converter circuit.

5. The windings of a dc machine are either

a. lap or wave connected
b. lap or spirally connected
c. wave or spirally connected
d. made of concentric coils or of short-pitched coils.

6. Critical field resistance of a dc generator is that value of the resistance at which

a. the field resistance line always lies below the OCC
b. the field resistance line is tangent to the OCC
c. the field resistance line crosses the OCC atleast at two points
d. the field resistance line does not touch the OCC at all.

7. The EMF induced in a four-pole dc generator having 1000 conductors, lap-connected
windings, flux per pole of 10 mwb and rotated at 600 rpm is

a. 1000 V
b. 500 V
c. 250 V
d. 100 V.

8. The brush and commutator arrangement in a dc motor is used to achieve

a. unidirectional current in the armature
b. unidirectional torque to achieve continuous rotation of the armature
c. change in the direction of rotation of the armature
d. high starting torque.

9. The number of parallel paths of the armature winding of an eight-pole, 250 V, wave wound dc