




Problemsolving strategy: effects of heat transfer
 Examine the situation to determine what type of heat transfer is involved.
 Identify the type(s) of heat transfer—conduction, convection, or radiation.
 Identify exactly what needs to be determined in the problem (identify the unknowns). A written list is useful.
 Make a list of what is given or what can be inferred from the problem as stated (identify the knowns).
 Solve the appropriate equation for the quantity to be determined (the unknown).
 For conduction, use the equation
$P=\frac{kA\text{\Delta}T}{d}$ .
[link] lists thermal conductivities. For convection, determine the amount of matter moved and the equation
$Q=mc\text{\Delta}T$ , along with
$Q=m{L}_{\text{f}}$ or
$Q=m{L}_{\text{V}}$ if a substance changes phase. For radiation, the equation
${P}_{\text{net}}=\sigma eA\left({T}_{2}{}^{4}{T}_{1}{}^{4}\right)$ gives the net heat transfer rate.
 Substitute the knowns along with their units into the appropriate equation and obtain numerical solutions complete with units.
 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
$40\phantom{\rule{0.2em}{0ex}}\text{\xb0}\text{C}$ than when it is at the temperature
$20\phantom{\rule{0.2em}{0ex}}\text{\xb0}\text{C}$ ?
The radiated heat is proportional to the fourth power of the
absolute temperature . Because
${T}_{1}=293\phantom{\rule{0.2em}{0ex}}\text{K}$ and
${T}_{2}=313\phantom{\rule{0.2em}{0ex}}\text{K}$ , the rate of heat transfer increases by about 30% of the original rate.
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Summary
Questions & Answers
it is the work done in moving a charge to a point from infinity against electric field
what is the weight of the earth in space
As w=mg where m is mass and g is gravitational force... Now if we consider the earth is in gravitational pull of sun we have to use the value of "g" of sun, so we can find the weight of eaeth in sun with reference to sun...
Prince
g is not gravitacional forcé, is acceleration of gravity of earth and is assumed constante. the "sun g" can not be constant and you should use Newton gravity forcé. by the way its not the "weight" the physical quantity that matters, is the mass
Jorge
Yeah got it... Earth and moon have specific value of g... But in case of sun ☀ it is just a huge sphere of gas...
Prince
Thats why it can't have a constant value of g
....
Prince
not true. you must know Newton gravity Law . even a cloud of gas it has mass thats al matters. and the distsnce from the center of mass of the cloud and the center of the mass of the earth
Jorge
please why is the first law of thermodynamics greater than the second
define electric image.obtain expression for electric intensity at any point on earthed conducting infinite plane due to a point charge Q placed at a distance D from it.
explain the lack of symmetry in the field of the parallel capacitor
pls. explain the lack of symmetry in the field of the parallel capacitor
Phoebe
does your app come with video lessons?
Vector is a quantity having a direction as well as magnitude
Damilare
tell me about charging and discharging of capacitors
a big and a small metal spheres are connected by a wire, which of this has the maximum electric potential on the surface.
3 capacitors 2nf,3nf,4nf are connected in parallel... what is the equivalent capacitance...and what is the potential difference across each capacitor if the EMF is 500v
equivalent capacitance is 9nf nd pd across each capacitor is 500v
santanu
four effect of heat on substances
why we can find a electric mirror image only in a infinite conducting....why not in finite conducting plate..?
because you can't fit the boundary conditions.
Jorge
what is the dimensions for VISCOUNSITY (U)
Branda
the study of heat an other form of energy.
John
heat is internal kinetic energy of a body but it doesnt mean heat is energy contained in a body because heat means transfer of energy due to difference in temperature...and in thermodynamics we study cause, effect, application, laws, hypothesis and so on about above mentioned phenomenon in detail.
ing
It is abranch of physical chemistry which deals with the interconversion of all form of energy
Vishal
it is a low studied the force between 2 charges F=q.q`\r.r
Mostafa
what is the formula of del in cylindrical, polar media
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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