Conduction Definition and 423 Threads

Thermal conduction is the transfer of internal energy by microscopic collisions of particles and movement of electrons within a body. The colliding particles, which include molecules, atoms and electrons, transfer disorganized microscopic kinetic and potential energy, jointly known as internal energy. Conduction takes place in all phases: solid, liquid, and gas.
Heat spontaneously flows from a hotter to a colder body. For example, heat is conducted from the hotplate of an electric stove to the bottom of a saucepan in contact with it. In the absence of an opposing external driving energy source, within a body or between bodies, temperature differences decay over time, and thermal equilibrium is approached, temperature becoming more uniform.
In conduction, the heat flow is within and through the body itself. In contrast, in heat transfer by thermal radiation, the transfer is often between bodies, which may be separated spatially. Also possible is the transfer of heat by a combination of conduction and thermal radiation. In convection, the internal energy is carried between bodies by a moving material carrier. In solids, conduction is mediated by the combination of vibrations and collisions of molecules, of propagation and collisions of phonons, and of diffusion and collisions of free electrons. In gases and liquids, conduction is due to the collisions and diffusion of molecules during their random motion. Photons in this context do not collide with one another, and so heat transport by electromagnetic radiation is conceptually distinct from heat conduction by microscopic diffusion and collisions of material particles and phonons. But the distinction is often not easily observed unless the material is semi-transparent.
In the engineering sciences, heat transfer includes the processes of thermal radiation, convection, and sometimes mass transfer. Usually, more than one of these processes occurs in a given situation.
The conventional symbol for thermal conductivity is k.

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  1. Somefantastik

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    Hey all, This is the equation of heat conduction in my PDE textbook: \int ^{t_{2}}_{t_{1}} \int\int\int_{A} [c \rho \frac{\partial u}{\partial t} - \nabla \dot \left( k \nabla u \right)]dxdydzdt = 0. where c is specific heat, rho is density, A is the subregion bounded by a smooth...
  2. K

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    How do I solve for the temperature at a certain time for conduction through a spherical shell? I have a shell 5 cm thick with a radius of 0.5m. I am starting with Q=KA(T2-T1)/L and I am completely lost as to where to go with it. Thanks!
  3. R

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  4. U

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  5. A

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  6. R

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  7. I

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  8. S

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  9. R

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  10. J

    How Far from a Conductor Is a Magnetic Field of 3.1x10^-5T?

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  11. S

    Calculating Heat Energy in Conduction: A Mars Case Study

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  12. A

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  13. O

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  14. C

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  15. P

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  16. P

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  17. P

    Calculating Entropy Change of a Wire Conduction

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  18. M

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  19. T

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  20. B

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  21. L

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  22. S

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  23. J

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  24. B

    Why is the Term Equivalent to (4/3)x in Conduction Electron Ferromagnetism?

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  25. S

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  26. A

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  27. E

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  28. M

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  29. O

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  30. L

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  31. C

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  32. G

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  33. D

    Question about heat conduction equation.

    I know how to solve a 1-D heat conduction equation when both ends are kept at 0 temperature(using separation of variables and Fourier series.). In the notes, the prof asked us to solve for one end kept at zero and the other insulated (at x=L) and referred to a non-existent chapter in our...
  34. T

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  35. J

    Conduction of Heat through a Material

    Homework Statement .005 m of Ice is in contact with .0015 m of Aluminum. The temp of the Ice is -10.0 degrees C, and the temp of the Aluminum is -25.0 degrees C. I need to calculate the heat per second per square meter that is conducted through the Ice - Aluminum combination Homework...
  36. A

    Solving Two Identical Conduction Spheres Problem

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  37. R

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    Homework Statement Calculate how many conduction electrons pass through a given area per second when a current of 1A flows. Homework Equations Current density, j = i/A (i=current, A=cross sectional area) Current desntiy, j = nevD (n=no of electrons per unit volume, e=charge on...
  38. A

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    Homework Statement The elements of a boiling water nuclear reactor consist of long cylindrical rods of uranium dioxide (U02) of diameter 8mm surrounded by a thin layer of aluminium cladding. In the reactor core the elements are cooled by boiling water at 285°C with a heat transfer...
  39. M

    Why Are Some Materials Better Conductors/Insulators than Others?

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  40. W

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  41. S

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  42. C

    What factors affect the electric field around a charged conduction sphere?

    Ok for example, if a solid conduction sphere was charged to 500volts and had radius of 1cm. Then charge, Q = VR = 5? So the E field just outside the sphere would be E = (1/4pi epsilon) x charge/R^2 = 4.5 x 10^14? Or am i getting confused?
  43. K

    Completely filled conduction band

    Hi all, From Pauli's principles, electrons cannot move into an already filled state. If i assume that somehow I fill in all the energy states in the conduction band (Population inversion :confused: )and then apply an electric field what happens?? Thanks...
  44. G

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    A solid sphere of radius a is immersed in a vat of fluid at a temperature T_0. Heat is conducted into the sphere according to dT/dt = D(d^2T/dr^2) (d-> partial derivative btw) If the temperature at the boundary is fixed at T_0 and the initial temperature of the sphere is T_1, find the...
  45. D

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  46. J

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  47. B

    Human Conduction: Exploring Electric Shock

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  48. Amith2006

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  49. E

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  50. M

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