Nanoscale sensors and energy devices – MCQs – EE

1. Nanoscale sensors operate based on changes in:
(A) Magnetic field
(B) Atomic or molecular properties at the nanoscale
(C) Light reflection only
(D) Acoustic waves

2. The sensitivity of nanosensors increases mainly due to:
(A) Large surface-to-volume ratio
(B) Small surface area
(C) Low conductivity
(D) Heavy mass

3. Carbon nanotube (CNT) sensors are primarily used for detecting:
(A) Gases and biomolecules
(B) Light reflection
(C) Mechanical pressure only
(D) Magnetic resonance

4. The working principle of nanosensors is often based on:
(A) Change in electrical, optical, or mechanical properties
(B) Increase in size of material
(C) Heat emission
(D) Magnetic coupling

5. A nanosensor converts:
(A) A physical or chemical signal into an electrical signal
(B) Heat into motion
(C) Light into heat
(D) Magnetic field into sound

6. Nanowire-based sensors are advantageous because they:
(A) Have high sensitivity and fast response
(B) Are heavy and stable
(C) Work only at high temperatures
(D) Require high power

7. Graphene-based sensors are preferred due to:
(A) High electrical conductivity and flexibility
(B) High density and brittleness
(C) Poor electron mobility
(D) High magnetic losses

8. In biosensors, nanomaterials enhance performance by:
(A) Increasing surface interaction with biomolecules
(B) Blocking chemical reactions
(C) Decreasing sensor lifetime
(D) Absorbing heat

9. Quantum dot sensors are useful in:
(A) Fluorescence-based optical detection
(B) Power electronics
(C) Heat generation
(D) Magnetic recording

10. Nanoscale energy devices mainly focus on:
(A) Energy harvesting, storage, and conversion at nanoscale
(B) Reducing energy usage only
(C) Electrical insulation
(D) Heat emission control

11. Nanogenerators produce electricity using:
(A) Mechanical vibrations or motion
(B) Magnetic flux only
(C) Thermal expansion
(D) Light reflection

12. The piezoelectric nanogenerator converts:
(A) Mechanical energy into electrical energy
(B) Electrical energy into heat
(C) Thermal energy into sound
(D) Magnetic energy into motion

13. Triboelectric nanogenerators (TENGs) operate based on:
(A) Contact electrification and electrostatic induction
(B) Magnetic field induction
(C) Thermal radiation
(D) Optical interference

14. Nanostructured solar cells improve efficiency by:
(A) Enhancing light absorption and charge transport
(B) Reducing electron mobility
(C) Blocking sunlight
(D) Increasing reflection

15. Quantum dot solar cells have tunable:
(A) Bandgap and absorption spectra
(B) Size only
(C) Temperature coefficient
(D) Magnetic properties

16. Nanostructured electrodes in batteries improve:
(A) Charge storage and conductivity
(B) Weight and cost
(C) Resistance and inefficiency
(D) Thermal noise

17. Lithium-ion batteries use nanomaterials to:
(A) Enhance electrode surface area and energy density
(B) Reduce conductivity
(C) Decrease voltage
(D) Block ion flow

18. Supercapacitors with nanomaterials show:
(A) High power density and long cycle life
(B) Low efficiency
(C) High internal resistance
(D) Poor charge retention

19. Graphene-based supercapacitors are effective due to:
(A) Large surface area and high conductivity
(B) Low surface area
(C) Poor electron transport
(D) Brittle structure

20. Hydrogen storage materials at nanoscale offer:
(A) High storage capacity and fast kinetics
(B) Low hydrogen absorption
(C) High leakage rates
(D) Poor mechanical strength

21. Thermoelectric nanomaterials convert:
(A) Temperature difference into electrical energy
(B) Light into mechanical energy
(C) Magnetic energy into heat
(D) Pressure into sound

22. Nanostructuring thermoelectric materials helps in:
(A) Reducing thermal conductivity and enhancing performance
(B) Increasing resistivity
(C) Decreasing efficiency
(D) Blocking charge carriers

23. The performance of nanoscale devices is strongly affected by:
(A) Quantum confinement and surface effects
(B) Large-scale geometry
(C) Macroscopic deformation
(D) Magnetic hysteresis

24. Nanosensors used in environmental monitoring detect:
(A) Toxic gases and pollutants
(B) Light intensity only
(C) Sound frequency
(D) Humidity alone

25. Plasmonic nanosensors rely on:
(A) Localized surface plasmon resonance (LSPR)
(B) Magnetic flux linkage
(C) Heat dissipation
(D) Acoustic vibration

26. Nanostructured fuel cells improve performance by:
(A) Increasing catalytic surface area and ion transport
(B) Decreasing conductivity
(C) Reducing electron flow
(D) Increasing thermal resistance

27. Self-powered nanosensors obtain energy from:
(A) Ambient mechanical, thermal, or solar energy
(B) External batteries
(C) AC power supply
(D) Magnetic field sources

28. ZnO nanowires are widely used in:
(A) Piezoelectric and gas sensing applications
(B) Magnetic resonance imaging
(C) Optical mirrors
(D) Electrical insulation

29. Nanostructured catalysts in energy devices help in:
(A) Enhancing reaction rate and energy conversion efficiency
(B) Slowing down chemical reactions
(C) Increasing energy loss
(D) Decreasing surface reactivity

30. The key advantage of nanoscale energy devices is:
(A) High efficiency, portability, and low material consumption
(B) High energy loss and large size
(C) Poor control and short life
(D) Heavy weight and complex structure