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VICPhysicsQuick questions

Unit 1: How is energy useful to society?

Quick questions on Thermodynamics and heat transfer: VCE Physics Unit 1 Year 11

12short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is conduction?
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Heat flow through a material by particle vibration and collision. Solids conduct best; gases conduct poorly. Metals are excellent conductors due to free electrons.
What is convection?
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Heat transfer by bulk movement of a fluid (liquid or gas). Hot fluid is less dense, rises; cold fluid sinks. Drives weather, ocean currents, the slow circulation of the Earth's mantle.
What is radiation?
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Heat transfer by electromagnetic waves (infrared mainly). Does not require a medium. Stefan-Boltzmann law: P=σAT4P = \sigma A T^4 where σ=5.67×10−8\sigma = 5.67 \times 10^{-8} W m−2^{-2} K−4^{-4}, AA surface area, TT absolute temperature.
What is energy balance?
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Earth absorbs sunlight (∼1370\sim 1370 W/m2^2 at the top of atmosphere, with about 30% reflected). The absorbed energy is re-emitted as infrared. Greenhouse gases absorb some of this infrared and re-radiate it (some down to the surface, some up).
What is natural greenhouse effect?
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Without it, Earth's surface would average about -18 degrees C. With it, about +15 degrees C. Life as we know it depends on the natural greenhouse effect.
What is enhanced greenhouse effect?
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Human activities (fossil fuel burning, deforestation, agriculture) have increased atmospheric CO2 from approximately 280 ppm (pre-industrial) to over 420 ppm (2024). The enhanced greenhouse effect drives observed climate change.
What is climate sensitivity?
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A doubling of CO2 from pre-industrial values is estimated to produce 2.5 to 4 degrees C of warming at equilibrium.
What is wrong specific heat capacity?
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Different materials have very different values. Use the value for the correct substance.
What is greenhouse effect confused with ozone depletion?
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Different phenomena. The greenhouse effect is about heat trapping. Ozone depletion is about UV transmission through the upper atmosphere.
What is q1?
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State the three mechanisms of heat transfer and identify the dominant mechanism in air at low velocity. [3 marks]
What is q2?
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A 22 kg copper block at 200∘200^\circC is placed in 44 kg of water at 20∘20^\circC in an insulated container. Take cCu=385c_{\rm Cu} = 385 and cwater=4186c_{\rm water} = 4186 J kg−1^{-1} K−1^{-1}. Calculate the equilibrium temperature.
What is q3?
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Refer to the Olympic Park thermal store. (a) Define latent heat of fusion. (b) Calculate the energy stored when 50005000 kg of salt-hydrate melts at 32∘32^\circC with Lf=230L_f = 230 kJ kg−1^{-1}.

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