1
GATE EE 2005
MCQ (Single Correct Answer)
+2
-0.6
Two magnetic poles revolve around a stationary armature carrying two coils ($$c_1-c'_1$$ , $$c_2-c'_2$$ ) as shown in Figure. Consider the instant when the poles are in a position as shown. Identify the correct statement regarding the polarity of the induced emf at this instant in coil sides $$c_2$$ and $$c_1$$. GATE EE 2005 Electrical Machines - D.C Machines Question 57 English
A
$$\odot\;in\;c_1$$, no emf in c2
B
$$\otimes\;in\;c_1$$, no emf in c2
C
$$\odot\;in\;c_2$$, no emf in c1
D
$$\otimes\;in\;c_2$$, no emf in c1
2
GATE EE 2005
MCQ (Single Correct Answer)
+2
-0.6
In relation to DC machines, match the following and choose the correct combination.

Group-I(Performance variables)
(P) Armature emf (E)
(Q) Developed torque (T)
(R) Developed power (P)

Group-II(Proportional to)
1.Flux ($$\phi$$), speed ($$\omega$$) and armature current ($$I_a$$)
2.$$\phi$$ and $$\omega$$ only
3.$$\phi$$ and $$I_a$$ only
4.$$I_a$$ and $$\omega$$ only
5.$$I_a$$ only

A
$$\begin{array}{l}P\;\;\;\;Q\;\;\;\;R\\3\;\;\;\;\;3\;\;\;\;\;1\end{array}$$
B
$$\begin{array}{l}P\;\;\;\;Q\;\;\;\;R\\2\;\;\;\;\;5\;\;\;\;\;4\end{array}$$
C
$$\begin{array}{l}P\;\;\;\;Q\;\;\;\;R\\3\;\;\;\;\;5\;\;\;\;\;4\end{array}$$
D
$$\begin{array}{l}P\;\;\;\;Q\;\;\;\;R\\2\;\;\;\;\;3\;\;\;\;\;1\end{array}$$
3
GATE EE 2005
MCQ (Single Correct Answer)
+2
-0.6
A 50 kW dc shunt motor is loaded to draw rated armature current at any given speed. When driven
(i) at half the rated speed by armature voltage control and
(ii) at 1.5 times the rated speed by field control, the respective output powers delivered by the motor are approximately
A
25 kW in (i) and 75 kW in (ii)
B
25 kW in (i) and 50 kW in (ii)
C
50 kW in (i) and 75 kW in (ii)
D
50 kW in (i) and 50 kW in (ii)
4
GATE EE 2004
MCQ (Single Correct Answer)
+2
-0.6
The armature resistance of a permanent magnet dc motor is 0.8 $$\Omega$$. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A form the same source will be
A
48.0%
B
57.1%
C
59.2%
D
88.8%
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