11. The slots used in the Induction motor are ___________
A. Semi-closed
B. Closed
C. Vacuum
D. Open
Answer: A
The slots used in the Induction motor are semi-closed. Open slots are used in the synchronous machine. Semi-closed slots have moderate air gap and lesser flux leakage.
12. The slots used in the Synchronous machines are ___________
A. Closed
B. Semi-open
C. Vacuum
D. Open
Answer: D
The slots used in the Synchronous machine are open. Open slots have a higher air gap and minimum flux leakage. The maximum power transfer capability increase due to a decrease in the leakage reactance.
13. The unbalanced set of 3-phase voltages causes ________
A. Positive sequence current
B. Negative sequence current
C. Zero sequence current
D. Half sequence current
Answer: B
The unbalanced set of 3-phase voltages causes a negative sequence current. The magnetic field generated due to the negative sequence current is in the opposite direction to the fundamental magnetic field. This induces double the frequency current in the rotor side which causes overheating of the motor.
14. The ratio of the rotor gross power and air gap power is _______
A. s
B. 1-s
C. 1+s
D. 0
Answer: B
The ratio of the rotor gross power and air gap power is 1-s.
The air gap power in the induction motor is Pg and the rotor gross power is (1-s)×Pg. The ratio is 1-s.
15. Reactive power is positive in the case of the capacitor.
A. True
B. False
Answer: B
The reactive power is defined as the product of the voltage, current, and sine of the difference between the phase angle of voltage and current. In the case of a capacitor, the voltage lags the current. The value of sine is negative and reactive power is negative.
16. The sine function is an odd function.
A. True
B. False
Answer: A
The odd functions are those functions that are symmetric about the origin. The sine function is an odd function whose time period is 2π.
17. The cosine function is an even function.
A. True
B. False
Answer: A
The even functions are those functions that are a mirror image of the y-axis. The cosine function is an even function whose time period is 2π.
18. Full form of NENO.
A. Neither even nor odd
B. Neither energy nor odd
C. Neither even nor original
D. Neither even nor orthogonal
Answer: A
NENO stands for Neither even nor odd. The functions which are not the mirror image of the y-axis and not symmetric about the origin are NENO functions.
19. The characteristics shown by an element in the V-I curve are V=Is(1-e-V/K). The nature of the element is _______
A. Non-linear, Bilateral, Passive
B. Linear, Unilateral, Active
C. Linear, Bilateral, Passive
D. Non-linear, Unilateral, Passive
Answer: D
The nature of the element is non-linear, unilateral, and passive. The shape of the characteristic is exponential rising. It should be symmetrical in the first and third quadrants for bilateral nature. Its slope is positive in the first quadrant which determines its passive nature.
20. Calculate the resonant frequency if the values of the capacitor and inductor are 2 F and 2 H.
A. .5 rad/sec
B. .6 rad/sec
C. .8 rad/sec
D. .9 rad/sec
Answer: A
During resonance condition XL=Xc. The value of the resonant frequency is
1÷√LC=1÷√4=.5 rad/sec.
The voltage across the capacitor and inductor becomes equal.
