Load Torques that Vary with Time MCQ [Free PDF] – Objective Question Answer for Load Torques that Vary with Time Quiz

11. The generated e.m.f from 25-pole armature having 200 conductors driven at 10 rev/sec having flux per pole as 20 mWb, with two parallel paths is ___________

A. 400 V
B. 500 V
C. 200 V
D. 300 V

Answer: B

The generated can be calculated using the formula

Eb = Φ×Z×N×P÷60×A,

Where

Φ represents flux per pole
Z represents the total number of conductors
P represents the number of poles,
A represents the number of parallel paths
N represents speed in rpm

Eb = .02×25×200×600÷60×2= 500 V. 

 

12. The unit of the flux is Weber.

A. True
B. False

Answer: A

Flux is the total amount of magnetic field lines passing through a given area. Φ is a dot product of magnetic flux density and area. The unit of the flux is Weber (WB). 

 

13. Which of the following motor can be referred to as a universal motor?

A. DC shunt motor
B. DC compound motor
C. Permanent magnet motor
D. DC series motor

Answer: D

DC series motor can operate on DC and AC. It is a universal motor. Universal motors are those motors that can operate on both DC and AC. DC shunt motor can only operate on DC because of pulsating torque in AC. 

 

14. The phase difference between voltage and current in the inductor.

A. 45°
B. 90°
C. 80°
D. 55°

Answer: B

In the case of an inductor, the voltage leads the current by 90°, or the current lags the voltage by 90o. The phase difference between voltage and current is 90°. 

 

15. The phase difference between voltage and current in the resistor.

A. 85°
B. 90°
C. 0°
D. 5°

Answer: C

In the case of a resistor, the voltage and current are in the same phase. The phase difference between voltage and current is 0°. The voltage drop in the resistor is given as V=IR. 

 

16. The phase difference between voltage and current in the capacitor.

A. 90°
B. 80°
C. 95°
D. 91°

Answer: A

In the case of a capacitor, the voltage lags the current by 90°, or the current leads the voltage by 90o. The phase difference between voltage and current is 90°. 

 

17. The slope of the I-V curve is 30°. Calculate the value of resistance. Assume the relationship between I and V is a straight line.

A. 1.732 Ω
B. 2.235 Ω
C. 1.625 Ω
D. 1.524 Ω

Answer: A

The slope of the I-V curve is reciprocal to resistance. The slope given is

30° so R=1÷tan(30°)=1.732 Ω.

The slope of the V-I curve is resistance. 

 

18. What is a mark to space ratio?

A. Ton÷Toff
B. Ton÷(Ton- Toff)
C. Ton÷2×(Ton×Toff)
D. Ton÷2×Toff

Answer: A

Mark to space is Ton÷Toff. It is the ratio of the time for which the system is active and the time for which is inactive. It has no unit. 

 

19. What is the formula for the moment of inertia? (m – a mass of the body, r – distance from the axis of the rotation)

A. ∑miri2
B. ∑miri
C. ∑miri4
D. ∑miri3

Answer: A

The moment of inertia is the property by the virtue of which the body withstands the effect of angular acceleration. It depends on the shape and mass distribution of the body. 

 

20. The generated e.m.f from 50-pole armature having 400 conductors driven at 20 rev/sec having flux per pole as 30 mWb, with lap winding is ___________

A. 230 V
B. 140 V
C. 240 V
D. 250 V

Answer: C

The generated can be calculated using the formula

Eb = Φ×Z×N×P÷60×A

Where

Φ represents flux per pole
Z represents the total number of conductors
P represents the number of poles
A represents the number of parallel paths
N represents speed in rpm.

In lap winding number of parallel paths are equal to the number of poles.

Eb = .03×50×400×1200÷60×50= 240 V. 

 

21. The unit of the moment of inertia is Kgm2.

A. True
B. False

Answer: A

The moment of inertia is taken as the sum of the product of the mass of each particle with the square of their distance from the axis of the rotation. The unit of the moment of inertia is kg×m2=kgm2

 

22. Calculate the moment of inertia of the egg having a mass of 7 kg and a radius of 44 cm.

A. .968 kgm2
B. 1.454 kgm2
C. 1.545 kgm2
D. 1.552 kgm2

Answer: D

The moment of inertia of the egg can be calculated using the formula

I=∑miri2.

The mass of the egg and radius is given

I=(7)×(.44)2=1.552 kgm2.

It depends upon the orientation of the rotational axis. 

Scroll to Top