Electrical Machine - I (3140913) MCQs

MCQs of DC Machines

Showing 71 to 80 out of 167 Questions
5 6 7 8 9 10
71.
Hopkinson test is conducted under which of the following condition?
(a) no load
(b) full load
(c) half load
(d) any of the above
Answer:

Option (b)

72.
The current drawn by the 230 V DC motor of armature resistance 0.5 Ω and back emf 200 V is
(a) 40
(b) 400
(c) 60
(d) 600
Answer:

Option (c)

73.
Which of the following methods are used to control the speed of DC motors is
(a) field current control
(b) armature circuit resistance control
(c) supply voltage control
(d) all of the above
Answer:

Option (d)

74.
A DC series motor is accidentally connected to single-phase ac supply voltage. The torque produced will be
(a) pulsating and unidirectional
(b) steady and unidirectional
(c) oscillating
(d) none of the above
Answer:

Option (a)

75.
What is the increase in the torque expressed as a percentage of initial torque, if current drawn by the dc series motor is increased from 10A to 11A?
(a) 10 %
(b) 11 %
(c) 21 %
(d) 1%
Answer:

Option (c)

76.
In a DC motor under constant terminal voltage, what is the relation between torque (T) and power (P)?
(a) T ∝ P
(b) T ∝ P²
(c) T ∝ P³
(d) T is independent of P
Answer:

Option (a)

77.
Slot wedges in a dc machine is made up of
(a) cast iron
(b) silicon steel
(c) fiber
(d) mild steel
Answer:

Option (c)

78.
For P pole machine relation between electrical degrees and mechanical degrees is
(a) θelec = (2/P) * θmech
(b) θelec = (P/2) * θmech
(c) θelec = θmech
(d) θelec = (4/P) * θmech
Answer:

Option (b)

79.
The air gap between the yoke and armature is dc machine is kept very small
(a) to avoid locking of the armature
(b) to avoid overheating
(c) to achieve a stronger magnetic field
(d) all of the above
Answer:

Option (c)

80.
A 4 pole dc generator is running at 1500 rpm the frequency of the current in the armature winding is __________ Hz.
(a) 50
(b) 100
(c) 150
(d) 200
Answer:

Option (a)

Showing 71 to 80 out of 167 Questions
5 6 7 8 9 10