106. If residual magnetism is present in a D.C. generator,
the induced e.m.f. at zero speed will be
(A) zero
(B) small
(C) the same as rated voltage
(D) high
Ans: A
107. Armature reaction in a generator results in
(A) demagnetisation of leading pole tip
and magnetisation of trailing pole tip
(B) demagnetisation of trailing pole tip
and magnetisation of leading pole tip
(C) damagnetising the centre of all poles
(D) magnetising the centre of all poles
Ans: A
108. Following energized winding of a D.C. machine should not
be opened as it would produce high inductive voltage which may be dangerous to
personnel and may cause its own insulation failure.
(A) Series field
(B) Compensating field
(C) Inter pole field
(D) Shunt field
Ans: D
109. Wave winding is composed of
(A) any even number of conductors
(B) any odd number of conductors
(C) that even number which is exact
multiple of poles + 2
(D) that even number which is exact
multiple of poles
Ans: C
110. The critical resistance of the D.C. generator is the
resistance of
(A) field
(B) brushes
(C) armature
(D) load
Ans: A
111. When two D.C. series generators are running in parallel,
an equilizer bar is used
(A) to increase the speed and hence
generated e.m.f.
(B) to increase the series flux
(C) so that two similar machines will
pass approximately equal currents to the load
(D) to reduce the combined effect of
ar-mature reaction of both machines
Ans: C
112. Which of the following generating machine will offer
constant voltage on all loads ?
(A) Self-excited generator
(B) Separately excited generator
(C) Level compounded generator .
(D) All of the above
Ans: C
113. Which of the following generators will be preferred if
they are required to be run in parallel ?
(A) Shunt generators
(B) Series generators
(C) Compound generators
(D) None of the above
Ans: A
114. Two generators are running in parallel. One of the generators
may run as motor for which of the following reasons ?
(A) The direction of that generator is
reversed
(B) The speed of that generator is
increased
(C) The field of that generator is
weakened
(D) That generator takes large share of
loads
Ans: D
115. A D.C. generator works on the principle of
(A) Lenz's law
(B) Ohm's law
(C) Faraday's law of electromagnetic
induction
(D) none of the above
Ans: C
116. A series generator can self-excite
(A) only if the load current is zero
(B) only if the load current is not zero
(C) irrespective of the value of load
current
(D) none of the above
Ans: B
117. A shunt generator can self-excite
(A) only if the resistance of the field
circuit is less than critical value
(B) only if the resistance of the field
circuit is greater than critical value
(C) irrespective of the value of the
resistance in the field circuit
(D)
only if the speed is less than critical value
Ans: A
118. The terminal voltage of a series generator is 150 V when
the load current is 5 A. If the load current is increased to 10 A, the terminal
voltage will be
(A) 150 V
(B) less than 150 V
(C) greater than 150 V
(D) none of the above
Ans: C
119. The open circuit voltage of a compound generator is 250
V. At full load the terminal voltage
(A) will be less than 250 V
(B) will always be 250 V
(C) may be greater or less than 250 V
(D) none of the above
Ans: C
120. Two D.C. shunt generators, each with armature resistance
of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total
current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265
V, their bus bar voltage will be
(A) 270 V
(B) 267.5 V
(C) 265 V
(D) 257.4 V
