11. Calculate the quality factor for the resistor.
A. inf
B. 0
C. 1
D. .7
Answer: B
The quality factor is defined as the ratio of the reactive power to the active power consumed. The resistor always absorbs active power. The value of reactive power consumed is 0.
Quality factor=0/P=0.
12. Selectivity value increases for lower values of bandwidths.
A. True
B. False
Answer: A
Bandwidth is defined as the range of frequencies for which the signal exists. Selectivity is inversely proportional to the bandwidth. Lower the bandwidth lower will be the cost.
13. Calculate the equivalent resistance when two resistances are connected in parallel of values 2 Ω, and 2 Ω.
A. 1 Ω
B. 2 Ω
C. 4 Ω
D. 7 Ω
Answer: A
When two resistances are connected in parallel their equivalent resistance is equal to the harmonic mean of the individual resistances.
Req=R1.R2÷(R1+R2)=22 Ω.
14. Calculate the equivalent capacitance when two capacitors are connected in parallel of values 8 F, 7 F.
A. 15 F
B. 20 F
C. 40 F
D. 7 F
Answer: A
When two capacitances are connected in parallel their equivalent capacitance is equal to the sum of the individual capacitances.
Ceq=(C1+C2)=15 F.
15. Plugging is suitable for __________ type loads.
A. Gravitational
B. Electrostatic
C. Weightless
D. Leading
Answer: A
Plugging is suitable for gravitational-type loads. It halts the motor operation. It can reverse the direction of rotation of the motor. It can hold the motor at zero speed.
16. In DC shunt machine ∅ is directly proportional to ______.
A. True
B. False
Answer: B
In a shunt DC machine, the field winding is in parallel with the armature winding. The armature current flows through the armature winding.
IF∝∅∝Vt.
17. Braking resistance should be selected in order to limit the braking current.
A. True
B. False
Answer: A
During braking, a high current flows in the armature circuit. To limit the braking current a proper value of braking resistance should be selected.
18. Torque developed in the motor is ___________
A. KmΦIa
B. KmΦIa3
C. 2KmΦIa
D. KmΦIa2
Answer: A
The torque developed in the motor is directly proportional to the flux, machine constant, and armature current. It is mathematically represented as
T= KmΦIa.
19. Full form of TVR is _________
A. Terminal voltage reversal
B. Total voltage reversal
C. Terminal voltage redirect
D. Total voltage reversal
Answer: A
TVR stands for terminal voltage reversal. It is one of the methods of countercurrent braking of the DC shunt motor. It halts the motor rapidly and reverses its direction of rotation.
20. Calculate the current in DC shunt field winding using the following data: Ia=15 A, IL=21, R=22, N=484.
A. 4 A
B. 2 A
C. 7 A
D. 6 A
Answer: D
In the DC shunt motor, field windings are connected in parallel with the armature circuit.
IF=IL-Ia=11-5=6 A.
Motor current is the sum of field and armature current.
