Thermal Conductivity and Radiation - One Line Questions

1. The term 'emissivity' for a real surface ranges from: — 0 to 1
2. Which of the following objects would radiate the most thermal energy at the same temperature? — A dull, black sphere
3. In natural convection, the fluid movement is driven by: — Differences in density caused by temperature variations.
4. The rate of heat transfer by conduction through a plane wall is given by Fourier's Law. What is the term that represents the material's ability to conduct heat? — Thermal conductivity (k)
5. Which of the following is an example of heat transfer by radiation? — Feeling the warmth of a campfire without touching it.
6. The process of heat transfer through the bulk movement of a fluid (liquid or gas) is called: — Convection
7. Which phenomenon is responsible for the formation of sea breezes and land breezes? — Convection
8. The heating of the Earth's atmosphere by the Sun is primarily an example of: — Radiation
9. Which of the following can transfer heat through a vacuum? — Radiation
10. The primary mechanism of heat transfer within the Earth's mantle is believed to be: — Convection
11. Which of the following is NOT a mode of heat transfer? — Friction
12. Consider a room with a heater. The air near the heater rises, and cooler air moves in to take its place. This is an example of: — Natural convection
13. The heat from the Sun reaches the Earth across the vast vacuum of space mainly through: — Radiation
14. Thermos flasks (Dewar flasks) are designed to minimize heat transfer. Which mode of heat transfer is primarily reduced by the vacuum layer between the walls? — Conduction and Convection
15. In a liquid, heat transfer occurs primarily through: — Conduction and convection
16. When you stand in direct sunlight, you feel warm primarily due to: — Radiation from the Sun.
17. A good absorber of radiation is also a good: — Emitter
18. A metal spoon placed in hot soup becomes hot due to heat transfer by: —
19. The phenomenon where heat is transferred through solids by the vibration of atoms and the movement of free electrons is called: — Conduction
20. Which material is known for its exceptionally low thermal conductivity, making it a good insulator? — Styrofoam
21. Forced convection involves: — Heat transfer assisted by an external force like a fan or pump.
22. Which of the following is a common application of using materials with low thermal conductivity? — Insulation in refrigerators and buildings.
23. A person wearing dark clothing on a sunny day feels hotter than someone wearing white clothing primarily due to: — Greater absorption of solar radiation by the dark clothing.
24. In the context of heat transfer, emissivity is a property that describes: — How well a surface emits thermal radiation compared to a black body.
25. Wien's Displacement Law relates the peak wavelength of emitted radiation to the temperature of an object. As temperature increases, the peak wavelength: — Decreases
26. Which type of material has a very high thermal conductivity, allowing heat to pass through it easily? — Conductor
27. Which of the following statements about convection is true? — It involves the movement of heated fluid particles.
28. Which of the following is a characteristic of thermal radiation? — It travels at the speed of light.
29. Which factor significantly influences the thermal conductivity of a solid material? — Its density and molecular structure
30. Which law quantifies the maximum amount of thermal radiation that can be emitted by an object at a given temperature? — Stefan-Boltzmann Law
31. Which law describes the relationship between the temperature of a black body and the total energy radiated per unit surface area per unit time? — Stefan-Boltzmann Law
32. The color of a surface affects its ability to absorb and emit thermal radiation. A black, matte surface is generally a: — Good absorber and good emitter
33. The insulating layer of air trapped in clothing helps to reduce heat loss from the body mainly by minimizing: — Conduction and convection
34. The silvered surfaces inside a thermos flask are intended to: — Reduce heat loss by radiation.
35. Which of the following is a poor conductor of heat (a good insulator)? — Glass
36. In which state of matter is thermal conductivity generally the highest? — Solid
37. The wavelength of the emitted thermal radiation depends on the temperature of the object, according to: — Wien's Displacement Law
38. When a hot object cools down by losing energy to its surroundings, the rate of cooling depends on the temperature difference between the object and its surroundings, according to: — Newton's Law of Cooling
39. The term 'thermal resistance' is inversely related to: — Thermal conductance
40. Which of the following factors does NOT affect the rate of heat transfer by radiation? — Thermal conductivity of the surface material
41. The Stefan-Boltzmann Law states that the total energy radiated per unit surface area of a black body is proportional to: — The fourth power of the absolute temperature (T⁴)
42. Heat transfer through conduction primarily relies on: — The vibration and collision of particles within a substance.
43. Which of the following best defines thermal conductivity? — The measure of a substance's ability to transfer heat through conduction.
44. What is thermal radiation? — The emission of energy via electromagnetic waves due to the temperature of an object.
45. Which property of a material determines how much heat it can store per unit mass per degree Celsius? — Specific heat capacity
46. Materials with high thermal conductivity are used in: — Heat sinks
47. Why does a blacksmith heat the metal rim of a cartwheel before fitting it onto the wheel? — To cause thermal expansion, making it larger.
48. What is the role of fins in heat exchangers? — To increase the surface area available for convection and radiation.
49. When ice melts into water at 0°C, the heat absorbed is called latent heat. This heat transfer does not raise the temperature, but rather changes the state. This process is related to heat transfer but is distinct from conduction, convection, and radiation. — True, latent heat transfer is a separate primary mode.
50. The SI unit for thermal conductivity is: — Watt per meter Kelvin (W/m·K)
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