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You can explore a simulation of the greenhouse effect that takes the point of view that the atmosphere scatters (redirects) infrared radiation rather than absorbing it and reradiating it. You may want to run the simulation first with no greenhouse gases in the atmosphere and then look at how adding greenhouse gases affects the infrared radiation from the Earth and the Earth’s temperature.

Problem-solving strategy: effects of heat transfer

  1. Examine the situation to determine what type of heat transfer is involved.
  2. Identify the type(s) of heat transfer—conduction, convection, or radiation.
  3. Identify exactly what needs to be determined in the problem (identify the unknowns). A written list is useful.
  4. Make a list of what is given or what can be inferred from the problem as stated (identify the knowns).
  5. Solve the appropriate equation for the quantity to be determined (the unknown).
  6. For conduction, use the equation P = k A Δ T d . [link] lists thermal conductivities. For convection, determine the amount of matter moved and the equation Q = m c Δ T , along with Q = m L f or Q = m L V if a substance changes phase. For radiation, the equation P net = σ e A ( T 2 4 T 1 4 ) gives the net heat transfer rate.
  7. Substitute the knowns along with their units into the appropriate equation and obtain numerical solutions complete with units.
  8. Check the answer to see if it is reasonable. Does it make sense?

Check Your Understanding How much greater is the rate of heat radiation when a body is at the temperature 40 ° C than when it is at the temperature 20 ° C ?

The radiated heat is proportional to the fourth power of the absolute temperature . Because T 1 = 293 K and T 2 = 313 K , the rate of heat transfer increases by about 30% of the original rate.

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Summary

  • Heat is transferred by three different methods: conduction, convection, and radiation.
  • Heat conduction is the transfer of heat between two objects in direct contact with each other.
  • The rate of heat transfer P (energy per unit time) is proportional to the temperature difference T h T c and the contact area A and inversely proportional to the distance d between the objects.
  • Convection is heat transfer by the macroscopic movement of mass. Convection can be natural or forced, and generally transfers thermal energy faster than conduction. Convection that occurs along with a phase change can transfer energy from cold regions to warm ones.
  • Radiation is heat transfer through the emission or absorption of electromagnetic waves.
  • The rate of radiative heat transfer is proportional to the emissivity e . For a perfect blackbody, e = 1 , whereas a perfectly white, clear, or reflective body has e = 0 , with real objects having values of e between 1 and 0.
  • The rate of heat transfer depends on the surface area and the fourth power of the absolute temperature:
    P = σ e A T 4 ,

    where σ = 5.67 × 10 8 J/s · m 2 · K 4 is the Stefan-Boltzmann constant and e is the emissivity of the body. The net rate of heat transfer from an object by radiation is
    Q net t = σ e A ( T 2 4 T 1 4 ) ,

    where T 1 is the temperature of the object surrounded by an environment with uniform temperature T 2 and e is the emissivity of the object.

Questions & Answers

Why does the lines of force not touch each other 🇲🇲
Gbemisola Reply
what is unit
Rayyanu Reply
Please canu get more questions on electric field and electric flux please
Gbemisola
is electric field directly proportional to the squared of a distance
Benjamin Reply
No electric field is inversely proportional to the squared distance between the charges
Gbemisola
lets treat linear expansivity please
Ujah Reply
The bullet 2.00cm long is fired at 420/s and passes straight through a 10.0 cm thick board existing at 280 m/s.What is the average acceleration of the bullet through the board?
FAUSTINA
an unstretched spring is 12cm long .A load of 5N stretched it to 15cm .how long will it be under a load of 15N?
Morapeli
hi
Africa
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Benjamin
Benjamin how are u are u a freshman in the university
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like 100 level
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Africa
Compare the electric flux through the surface of a cube of side length a that has a charge q at its center to the flux through a spherical surface of radius a with a charge q at its center.
Shari Reply
please I want to know how to solve increase in length
Ujah
Why a charged capacitor has potential difference but not emf
Gideon Reply
what is the dimension symbol of temperature?
Keren Reply
what is the dimension symbol of temperature?
Keren
what's the meaning of enthalpy in terms of latent heat, internal energy, phase change
Anthony Reply
Enthalpy is the degree ofdisorderlinessof a substance
Gbemisola
how to convert Kelvin to centigrade
Sangeetha Reply
what is the s, p, d, f in this table
Sangeetha
s, p, d, f in this table
Sangeetha
what kind of table this
Vengata
Periodic table
Gbemisola
what are waves
KENNETH Reply
In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities
Abdikadir
Discuss how would orient a planar surface of area A in a uniform electric field of magnitude E0 to obtain (a) the maximum flux and (b) the minimum flux through the area.
KARAN Reply
I'm just doing the first 3 with this message. but thankyou for the time your obviously intending to support us with. viva la accumulation
Marcel
Find the net capacitance of the combination of series and parallel capacitors shown belo
jean Reply
what is ohm?
Sharafat Reply
calculate ideal gas pressure of 0.300mol,v=2L T=40°c
Viola Reply
what is principle of superposition
Jyoti Reply
Practice Key Terms 9

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Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
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