Top 350+ Solved Electrical Machine 1 MCQ Questions Answer
Q. In a D.C. generator
a. external resistance = internal char-acteristic - armature reaction
b. internal characteristic = magnetisation characteristic - ohmic drop
c. external characteristic = magnetisation characteristic - ohmic drop - armature reaction
d. magnetisation characteristic = external characteristic
Q. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave
a. will be zero
b. will be of 5 Hz
c. willbeof5xiVHz
d. will be of v Hz 5
Q. A 220 V D.C. generator is run at full speed without any excitation. Theopen circuit voltage will be
a. zero
b. about 2 V
c. about 50 V
d. 220V
Q. In a separately excited generator supplying rated load the armature reaction ,
a. is always present
b. is always absent
c. may be sometimes present
d. none of the above
Q. If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speedwill be
a. zero
b. small
c. the same as rated voltage
d. high
Q. 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
Q. 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
Q. 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
Q. The critical resistance of the D.C. generator is the resistance of
a. field
b. brushes
c. armature
d. load
Q. 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
Q. Which of the following generating machine will offer constant voltage on allloads ?
a. Self-excited generator
b. Separately excited generator
c. Level compounded generator .
d. All of the above
Q. Which of the following generators will be preferred if they are required to berun in parallel ?
a. Shunt generators
b. Series generators
c. Compound generators
d. None of the above
Q. Two generators are running in parallel. One of the generators may run asmotor 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
Q. 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
Q. 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