Heat Transfer
Physics · 50 practice questions
Conduction, convection and radiation as modes of heat transfer; temperature gradient, thermal conductivity and heat flux; effect of surface nature on radiated/absorbed energy; conductivities of common materials; the thermos flask; land and sea breeze; the combustion engine.
- Differentiate between conduction, convection and radiation, and solve problems on temperature gradient, thermal conductivity and heat flux.
- Assess the effect of surface nature on radiated/absorbed energy and compare conductivities of common materials.
- Relate the working of the thermos flask, land/sea breeze and internal combustion/jet engines.
Try a few questions
- Practice question 1
Convection cannot occur in a solid mainly because convection specifically requires
- A.the presence of free electrons within the material
- B.the bulk movement of a fluid (liquid or gas)
- C.a very high temperature difference across the material
- D.a vacuum, with no material medium present at all
Show the answer
B. the bulk movement of a fluid (liquid or gas)
Since solids cannot flow in bulk the way fluids do, true convection is not possible within a solid.
- Practice question 2
Light, shiny (polished) surfaces are generally
- A.worse reflectors of radiant heat than dark, matte surfaces
- B.better reflectors of radiant heat than dark, matte surfaces
- C.equally good at reflecting radiant heat as dark, matte surfaces
- D.completely unable to reflect any radiant heat
Show the answer
B. better reflectors of radiant heat than dark, matte surfaces
A polished, reflective surface bounces back much more incident radiant heat than a dark, matte one.
- Practice question 3
A greenhouse gas, such as carbon dioxide, absorbs and re-emits infrared radiation, contributing to the warming of
- A.the earth's oceans exclusively, with no effect on the atmosphere
- B.outer space, with no measurable effect on the earth itself
- C.only the polar regions of the earth, with no global effect
- D.the earth's atmosphere, in a process similar to the greenhouse effect
Show the answer
D. the earth's atmosphere, in a process similar to the greenhouse effect
This absorption and re-emission of infrared radiation by greenhouse gases is precisely what drives atmospheric warming on a global scale.
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