Supercapacitors and flywheel systems – MCQs – EE

1. Supercapacitors are also known as:
(A) Ultracapacitors
(B) Hyperbatteries
(C) Superbatteries
(D) Electrolytic capacitors

2. Supercapacitors store energy through:
(A) Chemical reactions
(B) Electrostatic charge separation
(C) Magnetic induction
(D) Thermal energy conversion

3. The energy density of supercapacitors is:
(A) Higher than batteries
(B) Lower than batteries but higher than regular capacitors
(C) Equal to lithium-ion batteries
(D) Same as flywheels

4. The power density of supercapacitors compared to batteries is:
(A) Lower
(B) Higher
(C) Same
(D) Negligible

5. The typical energy density range of a supercapacitor is:
(A) 1–10 Wh/kg
(B) 20–50 Wh/kg
(C) 100–250 Wh/kg
(D) 300–500 Wh/kg

6. The main advantage of supercapacitors is:
(A) Long charge/discharge cycle life
(B) High energy storage capacity
(C) Low cost
(D) Chemical stability

7. The dielectric material used in supercapacitors is typically:
(A) Oxide layer
(B) Electrolyte solution
(C) Insulating polymer
(D) Metal film

8. Supercapacitors can be fully charged within:
(A) Seconds
(B) Minutes
(C) Hours
(D) Days

9. The self-discharge rate of supercapacitors is:
(A) Very low
(B) Moderate
(C) High
(D) Zero

10. The voltage of an individual supercapacitor cell is typically limited to about:
(A) 1.2 V
(B) 2.7 V
(C) 3.7 V
(D) 12 V

11. In a flywheel energy storage system, energy is stored as:
(A) Chemical energy
(B) Thermal energy
(C) Rotational kinetic energy
(D) Gravitational potential energy

12. The kinetic energy stored in a flywheel is given by:
(A) ½ mv²
(B) ½ Iω²
(C) Iω
(D) mgh

13. The moment of inertia (I) of a flywheel depends on:
(A) Its shape and mass distribution
(B) Only its rotational speed
(C) Material strength
(D) The type of bearing used

14. Flywheel energy storage systems are best suited for:
(A) Long-term energy storage
(B) Short-term power applications
(C) Thermal management
(D) Chemical storage

15. The main loss in a flywheel system is due to:
(A) Air friction and bearing losses
(B) Chemical reaction
(C) Magnetic hysteresis
(D) Electrolysis

16. The efficiency of modern flywheel systems typically ranges between:
(A) 50–60%
(B) 70–80%
(C) 85–95%
(D) 30–40%

17. The maximum speed of a flywheel is limited by:
(A) Material strength and tensile stress
(B) Air resistance
(C) Motor torque
(D) Magnetic field intensity

18. High-speed flywheels usually operate in:
(A) Air
(B) Vacuum
(C) Water
(D) Nitrogen atmosphere

19. Magnetic bearings in flywheel systems are used to:
(A) Reduce friction losses
(B) Increase mass
(C) Slow down rotation
(D) Control temperature

20. The response time of a flywheel system is:
(A) Milliseconds
(B) Seconds
(C) Minutes
(D) Hours

21. The energy density of a flywheel system is generally:
(A) Higher than Li-ion batteries
(B) Lower than Li-ion but higher than supercapacitors
(C) Lower than both batteries and supercapacitors
(D) Equal to capacitors

22. Supercapacitors are commonly used in:
(A) Energy smoothing and regenerative braking
(B) Long-term storage
(C) Fuel cell replacements
(D) Power plant generation

23. The cycle life of a supercapacitor can exceed:
(A) 1,000 cycles
(B) 10,000 cycles
(C) 100,000 cycles
(D) 1 million cycles

24. Flywheel systems are often combined with batteries to form:
(A) Hybrid energy storage systems (HESS)
(B) Chemical storage units
(C) Power amplifiers
(D) Inverters

25. The specific energy of flywheel systems typically ranges between:
(A) 1–10 Wh/kg
(B) 20–80 Wh/kg
(C) 150–250 Wh/kg
(D) 300–400 Wh/kg

26. The specific power of flywheel systems can reach up to:
(A) 10 W/kg
(B) 100 W/kg
(C) 1,000–10,000 W/kg
(D) 100,000 W/kg

27. A major advantage of flywheel systems is:
(A) High cycle life and fast response
(B) Low cost
(C) High self-discharge rate
(D) Toxic materials

28. The self-discharge rate of flywheel energy storage is:
(A) Low
(B) Moderate
(C) High
(D) Zero

29. Supercapacitors bridge the gap between:
(A) Batteries and fuel cells
(B) Batteries and conventional capacitors
(C) Transformers and inverters
(D) Motors and generators

30. The main limitation of supercapacitors for large-scale energy storage is:
(A) Low energy density
(B) Low power density
(C) High cost
(D) High maintenance