UPRVUNL'21 EE: Daily Practices Quiz 11-Aug-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. D.C. shunt motors are used in those applications where ……… is required.
(a) high starting torque
(b) practically constant speed
(c) high no-load speed
(d) variable speed

Q2. Cumulatively compounded motors are used where we require ………
(a) variable speed
(b) poor speed regulation
(c) sudden heavy loads for short duration
(d) none of the above

Q3. For 20% increase in current, the motor that will give the greatest increase in torque
is ……. motor.
(a) shunt
(b) series
(c) cumulatively compounded
(d) differentially compounded

Q4. Dynamic impedance of a parallel tuned circuit is ……….
(a) L/CR
(b) RL/C
(c) L/C
(d) R/L

Q5. When the supply frequency is more than the resonant frequency in a parallel a.c
circuit, then circuit is…….
(a) Resistance
(b) capacitive
(c) inductive
(d) none of the above

Q6. A dc series motor drawing an armature current of I_a is operating under saturated magnetic conditions, torque developed in the motor is proportional to
(a) 1/Ia
(b) 1/Ia^2
(c) Ia^2
(d) Ia

SOLUTIONS
S1. Ans.(b)
Sol. Practically constant speed

S2. Ans.(c)
Sol. Cumulatively compounded motors are used where we require sudden heavy loads
for short duration

S3. Ans.(b)
Sol. Series motor because
T∝I_a^2 (Before saturation)

S4. Ans.(a)
Sol. Dynamic impedance of parallel tuned circuit =L/RC

S5. Ans.(b)
Sol. Capacitive

S6. Ans.(d)
Sol. We know Torque Tα ΦIa, As the motor is operating under saturation condition so torque will be independent of flux i.e., T α Ia.