Untitled Deck Flashcards
How does thermal energy flow?
Thermal energy flows from a region of higher temperature to a region of lower temperature.
What is conduction?
The transfer of thermal energy through a medium without any flow of the medium.
Why is conduction faster in copper than wood?
Copper has free electrons for quick heat transfer; wood is an insulator and lacks these electrons.
Why are air and liquids poor conductors of heat?
Their particles are far apart, making heat transfer through collisions difficult.
What is convection?
The transfer of thermal energy by convection currents in a fluid due to density differences.
How does heated water move during convection?
Heated water becomes lighter, rises, and cooler water sinks, creating a continuous flow.
What is conductivity?
The amount of heat flow in unit time that determines the thermal conductivity of a substance.
How does the length of a conductor affect heat flow?
Heat energy dissipated is inversely proportional to length.
How does the area of cross-section of a conductor affect heat flow?
Heat energy dissipated is directly proportional to the area.
How does temperature difference affect heat flow?
Heat energy dissipated is directly proportional to the temperature difference.
Define a conductor.
A material that allows electricity or heat to pass through easily.
Define an insulator.
A material that resists electricity or heat flow.
What is radiation?
Transfer of thermal energy in the form of electromagnetic waves without needing a medium.
Why can radiation occur in a vacuum, but conduction and convection cannot?
Radiation uses electromagnetic waves and doesn’t need a medium; conduction and convection do.
How do dark and rough surfaces affect heat transfer by radiation?
Dark and rough surfaces absorb and emit more heat.
How do light and shiny surfaces affect heat transfer by radiation?
Light and shiny surfaces reflect and absorb less heat.
How do color and texture affect infrared radiation emission and absorption?
Dull and black surfaces are better emitters and absorbers than shiny and silver surfaces.
How does surface area affect infrared radiation emission and absorption?
Larger surface areas emit or absorb infrared radiation at a higher rate.
How does surface temperature affect infrared radiation emission?
Higher surface temperatures result in a higher rate of emission.
What is the purpose of placing heating coils at the bottom of electric kettles?
To enable thermal energy transfer in water by convection.
How do greenhouses trap heat?
Infrared radiation enters, warms the inside, and longer wavelengths of radiation are trapped.
How do vacuum flasks minimize heat transfer?
By minimizing heat transfer by conduction, convection, radiation, and evaporation.
