What is Conduction: Definition and 423 Discussions

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.

View More On Wikipedia.org
Recent contents Top users
  1. G

    Is there a way to calculate thermal conduction speed or time?

    Hello. I'm working in the plasma physics and trying to calculate the thermal conduction time or speed. Thanks to the people here replied my questions, I was able to calculate the thermal conductivity of the plasma with the given electron temperature in SI unit...
  2. G

    2D heat conduction of layered composite model

    Hi, I am trying to formulate a 2D model to calculate the temperature change over time in a composite material. The material consists of several layers, and is heated from all edges by a known temperature vs time profile. I was thinking of creating a finite element model. Can someone...
  3. M

    What is the temperature at the wire/insulator interface?

    Homework Statement A cylindrical wire with radius ##r_i## carries a current ##I \frac{A}{cm^2}## with a resistance of ##\Omega \: ohms\times cm##. It is insulated with a material with radius ##r_o## whose thermal conductivity is ##k \frac{W}{cm \times K}##. The insulator is exposed to air that...
  4. F

    How Does Gas Pressure Affect Heat Conduction in a Vacuum Flask?

    Homework Statement A vacuum flask of radius r and length l consists of two concentric cylinders separated by a narrow gap containing a gas at pressure 10^-2 Nm^-2. The liquid in the flask is at 60 degrees Celcius and the air outside is at 20 degrees celcius. Estimate the rate of heat loss by...
  5. samgrace

    Question about QM description of metallic conduction

    I have read in a classical EM book: " The picture of conduction electrons moving freely in conductors is an oversimplification, although it gives a good qualitative description of many of the properties of electric current. In some materials the current is due to the motion of carriers...
  6. N

    Example for conduction, convection, radiation energies ?

    Can you guys give me example for conduction, convection, radiation energies ?
  7. N

    Assembling mass matrix for transient heat conduction pde

    I have derived the weak form of the transient heat conduction equation (for FEM) and I am having trouble trying to assemble the mass matrix This is the PDE: \frac{\partial U}{\partial t} = \alpha \nabla^2U This is the equation for the mass matrix for an element: M^e = \int \Psi...
  8. S

    Why does diode breakdown into conduction when reverse biased?

    why does diode breakdown into conduction when reverse biased?
  9. Feodalherren

    Temperature at junction of gold and silver bars?

    Homework Statement A bar of gold (Au) is in thermal contact with a bar of silver (Ag) of the same length and area (Fig. P20.39). One end of the compound bar is maintained at 80.0°C, and the opposite end is at 30.0°C. When the energy transfer reaches steady state, what is the temperature at...
  10. Y

    Question regarding conduction current

    Assume a voltage source connected to a capacitor which filled with a dielectric material having non zero conductivity, then, displacement current=conduction current of the wire=CdV/dt while conduction current density of the dielectric=σE=σV/d But considering dc source, displacement...
  11. T

    Peak rectifier - conduction interval

    Homework Statement I am confused about how they got the expression: VPcos(ωΔt)=VP-Vr Specifically you can find the notes in page 5 of this article: http://whites.sdsmt.edu/classes/ee320/notes/320Lecture8.pdf You may also find it useful to refer to the graphs as a reference...
  12. C

    Can someone tell me if conduction is more powerful than induction?

    Homework Statement In the lab I am writing about, here were the directions 7. Predictions: Touch a metal sphere to neutralize it. Holding the plastic handle, bring the metal sphere in contact with the charged foam slab. Do not touch the sphere at any time. Take the sphere away from the...
  13. TrickyDicky

    Displacement and conduction currents

    One thing that I don't intuitively get about these currents is that in the conduction current the electric field is supposed to be static at each point of the conductor(there is no assumption of current intensity change), whilst the displacement current is defined as a varying electric field...
  14. paulmdrdo

    Valence and conduction bands in an n-type material

    can you explain why the trivalent impurities exert lower forces on the outer-shell electrons than the pentavalent impurities? and why The valence and conduction bands in an n-type material are at slightly lower energy levels than the valence and conduction bands in a p-type material?
  15. U

    Thermal Flask, heat conduction

    Homework Statement Find an expression for thermal conductivity using kinetic theory. Given a vacuum flask of these dimensions, find the heat loss per unit time. Estimate the time taken for the water to cool down to 40 deg. Homework Equations The Attempt at a Solution...
  16. A

    Hole conduction vs electron conduction

    So recently I took a blow to my understanding of how hole conduction works. Like many others I had the idea that the hole i just an absence of an electron and when it moves the collection of electrons move opposite direction of it like in the analogy where the electron hole is an empty seat in...
  17. A

    What is the role of chemical potential in conduction?

    I am studying some simple models of how conduction arises on a microscopic level. A central idea is the following: Look at two leads attached by a conducting channel. Initially the system as a whole is in equilibrium which especially means that the chemical potential μ is the same everywhere...
  18. M

    Question in (Conduction ) A steel plate 2 cm thick

    Hi A steel plate 2 cm thick is maintained at a temperature of 550 C at one face and 50 C on the other . The thermal conductivity of stainless stress at 300 C is 19.1 W/mK . Compute the heat transferred through the material per unit length ? Answer : - we have q = - k . A ...
  19. B

    Conduction Angle in SCR Single Phase Rectifiers

    Hi all, When considering a half wave SCR rectifier (single phase) with an RL load, the term θ (conductive angle) appears in equations relating to the performance of the circuit. In terms what is physically happening in the circuit, what does θ actually represent?
  20. A

    Valence vs conduction band

    Why can't electrons move inside the valence band? Is that the Pauli exclusion principle - and is it true that the electrons can't move even when the valence band is only partially filled?
  21. B

    BOOST SMPS/Converter in Discontinuous Conduction Mode

    Homework Statement A boost SMPS has the following design properties: Input Voltage - Vi = 6.0v Maximum Output Current - Io(max) = 0.5A switching frequency - F = 100khz Inductor = 500μH Capacitor = 1000μF with ESR 25mΩ Consider the boost SMPS operating in discontinuous conduction...
  22. J

    Transient 1D radial conduction

    Morning all, This is probably going to seem absurdly simple, however I need to do a very quick conduction calculation as part of a much larger problem I am working on. I was wondering if anyone would be able to give me some pointers as time is of the essence. The scenario can be simplified as...
  23. Crazymechanic

    Exploring Electric Fields in Conductors: Spheres, Cages, and Beyond

    Ok again I'm thinking some things but a simple question, You have two metal spheres , one inside the other.Now we know long ago from Faraday that closed metal spheres or cages or etc that are at some potential above ground tend to have their charge at the outside of the conductor in this case...
  24. S

    Why Conduction Band? Understanding Its Significance

    Why are insulators supposed to possesses a "conduction band", even if usually empty? If you do take the energy to cross the "band gap" and displace an electron, just why should it become delocalized/conductive? Couldn´t it just lose energy rapidly by exciting phonons until it gets trapped...
  25. L

    Heat conduction increasing with temperature

    Do you know of any material/compound/alloy which have low coefficient of heat conduction at room temperature and higher one at greater temperatures?
  26. R

    Steady state conduction in a hollow sphere

    Hello, I'm having trouble with a conduction problem, I have access to the answer but not the solution. I did it on my own and my value is half of what the answer is. Now, my calculus is a little rusty, but I don't know where I am going wrong. So the dimensions and temperatures of the sphere...
  27. H

    Calculating B of inductor operating in continuous conduction mode?

    Hello everyone, I am working on a coil design and have a question. The coil is meant to operate in continuous conduction mode, so the current waveform is a ramp waveform. B=V*t / N*Ae When calculating V*t do I use 1/2 t (since the current only increases for the first half of the...
  28. J

    Thermal Conduction Homework: Find Rod's Conductivity

    Homework Statement A rod, with sides insulated to prevent heat loss, has one end immersed in boiling water at 100C and the other end immersed in a water/ice mixture at 0C. The rod has uniform cross-sectional area of 4.04 cm^2 and length 91cm. Under steady state conditions, heat conducted by...
  29. L

    What is the valance and conduction band?

    Hello, I am writing a technical essay on solar cells and I am having trouble finding out exactly what the valance and conduction band actually are. It's a bit elusive, the textbooks I am using simply state the two bands without explaining what they are. If anybody could provide any...
  30. T

    Why Can Electrons in the Conduction Band Move Around so Easily

    As my title states, I want to understand why electrons in the conduction band can move around so easily in the material. Is it due to the presence of many closely spaced (blurred out) energy levels which make it easy for the electrons to move around? Or are the electrons undergoing some kind...
  31. V

    A few simple questions about band structure and conduction

    Hi! I'm reading about band structure and conduction in regular crystals and semiconductors, and I've hit a few confusing points my book doesn't explain well enough for me. In one part, they're explaining conduction in a 1D crystal with lattice spacing a (and therefore reciprocal lattice...
  32. M

    Fourier Heat Conduction Law

    Homework Statement Problem 1.60. A frying pan is quickly heated on the stovetop to 200 C. It has an iron handle that is 20 cm long. Estimate how much time should pass before the end of the handle is too hot to grab with your bare hand. (Hint: The cross-sectional area of the handle doesn't...
  33. H

    Requirements for inductor to operate in continuous conduction mode?

    Question about continuous conduction mode converter I have a few quesitons about CCM converters I have posted a basic schematic of the circuit in question as an attachment. The circuit is a series LC circuit in which the inductor and capacitor charge during the on time. During the off time...
  34. X

    Exact solution of heat conduction equation

    Hi all, I am trying to find the exact solution of the 3D heat conduction equation. The problem I have is I have infinite large 3D body. Then the initial condition is : in the center it is a constant temperture T1; all the other places have temperature T2. The boundary condition is the center...
  35. S

    Rate of thermal conduction in various copper structures

    A cylinder is constructed from a super insulator. The dimensions of the cylinder are Length L: 1 M; inside diameter i.d.: 12 mm. The entire Length of the cylinder contains copper (cases described below). Heat (T > 100C) is continuously applied to the copper on one end of the cylinder...
  36. N

    Transient heat conduction in 1D solid

    1D solid, 0<x<L, with the following boundary conditions: The whole solid is at T = T1 at t=0. x = 0 is held constant at initial temperature T1 for all t. There is a constant flow of heat, dQ/dt out of the solid at x = L. T(0,t) = T1, T(L,0) = T1, How do we go about solving the heat equation...
  37. M

    MATLAB DC conduction equation in Matlab

    Hello I am solving DC conduction equation in Matlab. My equation is 1/r * ∂/∂r [r*σ* ∂V/∂r]=∂ρ/∂t My equation is 1D(only varies with radius) and time dependent. i am using pdepe solver.The space charge ( ρ) is the time dependent variable. But the form of MATLAB pdepe solver the time...
  38. heycoa

    Solid State Physics | electrons | thermal conduction

    Homework Statement Explain why electrons carry a net energy but not a net current in the case of thermal conduction. Homework Equations n/a The Attempt at a Solution n/a Please help me understand this!
  39. S

    Conduction between two materials

    When I have a metal object at 0 degrees and a plastic object at 0 degrees, the metal feels colder as heat is conducted away at a faster rate. The reason for that would be that the metal is a better conductor of heat so when my hand touches it, it can start vibrating more quickly than the...
  40. P

    What type of heat transfer is this? Conduction, convector, or radiation?

    We have a pan that is used to boil water. There are 2 surfaces to the pan. One is touching the water and the other is touching the stove, obviously. We have heat that is transferred to to pan's bottom. I know what all 3 are and process of elimination tells me this is conduction. Is it...
  41. A

    Solving Diode Conduction Homework with KCL, KVL, V=IR

    Homework Statement Use the approximation that the diodes conduct only at the indicated forward voltage. For what values of R is D2 Conducting and not conducting? Homework Equations KCL KVL V=IR The Attempt at a Solution I really am not sure how to approach this problem, as none...
  42. S

    Conduction band in Na metal

    Homework Statement Describe the ”conduction band” in Na metal. Why it is half-filled and non-magnetic? The Attempt at a Solution Na has electron configuration: [Ne]3s^1 the 3s band is highest in energy and is the conduction band for Na. since Na has 1 electron in the 3s band, and...
  43. S

    Thermal conduction between difference surfaces

    Homework Statement from this video: It showed that a better conductor of heat will transfer heat as well as absorb heat more quickly than a lousy conductor. However, during the transfer the heat is passed from eg metal at 30 degrees to a solid at 20 degrees . So why would the metal being a...
  44. I

    Difference betweem conduction and diffusion?

    On an undergrad engineering level of talk, is there any difference between conduction and diffusion ways of heat transfer? Conduction occurs because of the vibrational freedom of atoms. And diffusion is, I think, because of diffusing of atoms?
  45. L

    Charging by conduction with and odd net charge?

    Hello, I've just got a quick question about charging an object by conduction. I've been studying for my final and I came across a problem that I can't really see how to solve. Say you have two conducting spheres, A and B. They are both exactly the same in every way except for their electric...
  46. M

    Help calculating heat loss through transient conduction

    Homework Statement I have a stove, basically a metal drum which is the fuel chamber. Think of a hobo stove, just a metal drum with a fire in it. This stove creates convection heat via exhaust, and conductive heat to the metal drum itself which "slowly" releases the heat from there...now, I...
  47. O

    Electron In conduction band at 0K

    Electrons in the conduction band of metal will be attracted by the nucleus of atom? I wonder why there can be electron in the conduction band of metal at 0K .At 0K , all electron should lose its energy as(3/2)kT=0. Thank you
  48. E

    Conduction band splitting under spin/orbit coupling

    Hi, Does anyone have an intuitive idea of why it is always the valence bands split under spin/orbit coupling, but not conduction band? (or a much smaller splitting than valence band) I know through tight-binding calculations, if I plug in numbers correctly, conduction bands always have...
  49. O

    Semiconductor (hole in conduction band)

    Can a hole go to conduction band? In p-type, the hole is above the fermi level, lower than conduction band, higher than valence band, how can this be happened? And will this happen when the p-type is at 0K
  50. P

    How Does Heat Transfer Through Different Metals?

    Two 0.525 m rods, one lead and the other copper, are connected between metal plates held at 2.00°C and 106°C. The rods have a square cross section of 1.50 cm on a side. How much heat flows through the two rods in 1.0 s? Assume no heat is exchanged between the rods and the surroundings...
Back
Top