11. The shape of the current-torque characteristics in DC shunt motor is __________
A. Rectangular Hyperbola
B. Parabola
C. Straight line
D. Ellipse
Answer: C
The shape of the current-torque characteristics in the DC shunt motor is a straight line. The motor equation is
Eb=Vt-IaRa=Km∅ωm
T=Km∅Ia
∅∝If.
Torque ∝ Ia.
12. The relationship between the torque(T) and power(P) developed in the DC shunt motor is ___________ (Neglecting all the losses)
A. T ∝ √P
B. T ∝ P2
C. T ∝ ∛P
D. T ∝ P
Answer: D
The torque developed in the DC shunt motor is the ratio of power developed and the angular
speed of the motor
T=EbIa÷ωm=P÷ωm
T ∝ P.
13. The value of current at time of starting is ___________
A. High
B. Low
C. Very low
D. 0
Answer: A
At the time of starting the motor is at rest. The e.m.f developed in the motor is zero.
Ia×Ra = Vt-Eb. Ia=Vt÷Ra.
The starting current is very high about 10-15 times of full load current.
15. Calculate the bandwidth in a series RLC circuit if the frequency is 20 Hz and the quality factor is 5.
A. 2 Hz
B. 4 Hz
C. 6 Hz
D. 8 Hz
Answer: B
Bandwidth is defined as the range of frequencies for which the signal exists. Selectivity is inversely proportional to the bandwidth.
B.W(Hz)=f÷Q=20÷5=4 Hz.
16. The value of unit step function at t=5 sec is ________
A. 0
B. 1
C. -1
D. 2
Answer: B
The unit step function is discontinuous at t=0.
The value of the unit step function is 1
for t>0 and zero for t<0.
It is a right-handed and bounded signal.
17. The value of impulse at t=0 is __________
A. 0
B. 2
C. 1
D. infinite
Answer: D
The impulse function is neither an energy signal nor a power signal. It is a pulse of infinite amplitude and zero width. The value of impulse is 0 for time not equal to zero.
18. Full form of IFOC.
A. Indirect field-oriented control
B. Inverter field-oriented control
C. Isolated field-oriented control
D. Insight field-oriented control
Answer: A
IFOC stands for indirect field-oriented control. DTC and IFOC are the techniques used for controlling the speed and torque of a 3-phase induction motor.
19. The characteristic shown by an element in the I-V curve is a straight line passing through the origin with a positive slope. The nature of the element is _______
A. Non-linear, Bilateral
B. Linear, Unilateral
C. Linear, Bilateral
D. Non-linear, Unilateral
Answer: C
The nature of the element is linear and bilateral. It follows the principle of homogeneity and the law of additivity. It should be symmetrical in the first and third quadrant for bilateral nature.
20. Calculate the total energy stored in the inductor if the current value is 4 A and inductance values are 1 H and 2 H.
A. 72 J
B. 22 J
C. 82 J
D. 24 J
Answer: D
The energy stored in the inductor is
.5×Leq×I2.
The value of Leq=1+2=3 H.
The total amount of energy stored in the inductor in the steady-state condition.
