Energy conversion efficiency and optimization – MCQs – EE

1. Energy conversion efficiency is defined as the ratio of:
(A) Input energy to output energy
(B) Output energy to input energy
(C) Input power to output power
(D) Energy loss to energy gain

2. The efficiency of any energy conversion device is always:
(A) 100%
(B) Greater than 100%
(C) Less than 100%
(D) Negative

3. The major cause of energy losses in electrical machines is:
(A) Friction and windage
(B) Heat loss
(C) Magnetic losses
(D) All of the above

4. In a thermal power plant, the overall efficiency is typically about:
(A) 10–20%
(B) 25–35%
(C) 50–60%
(D) 70–80%

5. The efficiency of an ideal transformer is:
(A) 0%
(B) 50%
(C) 100%
(D) 75%

6. The main loss in an induction motor that reduces efficiency is:
(A) Copper loss
(B) Iron loss
(C) Stray loss
(D) All of the above

7. Generator efficiency mainly depends on:
(A) Magnetic flux
(B) Electrical load
(C) Mechanical input
(D) All of the above

8. The efficiency of a solar cell decreases primarily due to:
(A) Decrease in light intensity
(B) Increase in temperature
(C) Decrease in area
(D) Decrease in load

9. The efficiency of a wind turbine depends mainly on:
(A) Wind speed
(B) Blade design
(C) Air density
(D) All of the above

10. The Betz limit states that the maximum theoretical efficiency of a wind turbine is:
(A) 33.3%
(B) 45%
(C) 59.3%
(D) 75%

11. The efficiency of a hydroelectric power plant can reach up to:
(A) 30%
(B) 50%
(C) 70%
(D) 90%

12. The efficiency of a fuel cell is typically in the range of:
(A) 20–30%
(B) 40–60%
(C) 60–80%
(D) 90–100%

13. Which of the following helps in improving the efficiency of an electric motor?
(A) Reducing friction losses
(B) Using better insulation
(C) Operating near rated load
(D) All of the above

14. The thermal efficiency of a Carnot engine depends on:
(A) Working fluid only
(B) Temperature difference between source and sink
(C) Type of insulation
(D) Mechanical design

15. Regenerative braking improves the efficiency of:
(A) Transformers
(B) Electric vehicles
(C) Gas turbines
(D) Steam turbines

16. The main parameter to optimize in an energy system is:
(A) Input energy
(B) Output energy
(C) Energy loss
(D) System efficiency

17. The main objective of energy optimization is to:
(A) Increase system losses
(B) Reduce cost and improve performance
(C) Increase energy input
(D) Decrease output power

18. The energy efficiency of a device can be increased by:
(A) Improving material quality
(B) Better system design
(C) Proper maintenance
(D) All of the above

19. Power factor improvement in electrical systems leads to:
(A) Reduced losses
(B) Improved voltage regulation
(C) Higher efficiency
(D) All of the above

20. Energy losses in transmission lines are minimized by:
(A) Increasing current
(B) Decreasing voltage
(C) Increasing voltage and reducing current
(D) Reducing conductor size

21. Which of the following has the highest energy conversion efficiency?
(A) Solar cell
(B) Wind turbine
(C) Hydroelectric plant
(D) Steam power plant

22. Co-generation improves overall efficiency by:
(A) Using only mechanical energy
(B) Utilizing waste heat for useful work
(C) Reducing input energy
(D) Increasing transmission losses

23. The efficiency of thermal systems is generally low because of:
(A) High temperature losses
(B) Friction
(C) Entropy increase and heat rejection
(D) Mechanical design limitations

24. The overall efficiency of a combined cycle power plant can reach up to:
(A) 30%
(B) 45%
(C) 60%
(D) 75%

25. The ratio of useful output power to total input power is called:
(A) Load factor
(B) Power factor
(C) Efficiency
(D) Utilization factor

26. Optimization of energy systems aims to:
(A) Reduce efficiency
(B) Minimize energy wastage
(C) Increase operating costs
(D) Decrease power output

27. Exergy analysis is used to:
(A) Analyze mechanical strength
(B) Measure useful work potential of energy
(C) Determine input voltage
(D) Find system reliability

28. The main losses in power transformers are:
(A) Copper and iron losses
(B) Dielectric losses only
(C) Stray magnetic losses only
(D) Radiation losses

29. Maximum efficiency of a DC generator occurs when:
(A) Iron losses = Copper losses
(B) Copper losses > Iron losses
(C) Iron losses > Copper losses
(D) Armature current is zero

30. Energy audit is conducted to:
(A) Increase power demand
(B) Identify energy-saving opportunities
(C) Reduce generation capacity
(D) Increase power losses