Conduction Definition and 397 Threads

Consider the figure from section "Electrical conductivity":https://en.wikipedia.org/wiki/Valence_and_conduction_bands I understand that below the Fermi level, we have bands of allowed energy separated by band gaps. Then, we have the Fermi level. Then we have the conduction band. My question...

Molecules do not use magnetic energy as latent heat - adding magnetic energy does not cause a phase change. If electrical conduction indeed required energy state changes, then during electrical conduction, a change of energy state would likely consume magnetic energy as latent heat, instead of...

Suppose that a static electric field E is applied on a conductive crystal. Then, how quantum mechanics describes the electron movements in the crystal? I have been trying to find an explanation, but have not found any. As I understand it, we could treat the E field as a time-dependent...

Homework Statement Show that the conduction and displacement currents cancel each other for a spherical radioactive solid emitting charged particles radially outwards Homework Equations Maxwell's equations Current density (j) Displacement current density (jd) The Attempt at a Solution I...

I'm upgrading a non-PFC (power factor corrected) offline power supply design to include PFC for European deployment. The total output power is less than 25W, and the two output windings are around 20V. I'm familiar with boost-flyback topologies for isolated PFC supplies, but that seems to...

From gcsescience.com; "Heat can be transferred by conduction only in solids." Q. Doesn't conduction take place directly prior to convection (when a radiator heats up a room)? If my cold hand came into contact with the warm radiator this would cause conduction; why isn't it the same for the...

Why is the conduction band state s-type and the corresponding valence band state p-type?

conduction of electricity in electrolytes is due to presence of positive ions and negative ions or presence of positive ions, negative ions and electrons?

This is mainly just a theoretical question: say you have a rectangular box made of styrofoam (one of those ice cooler things) and it is levitating in air at room temperature conditions. It also has one hole at the top of the container so that heat can get out of it. Inside the box is a lightbulb...

Given that we know the affected root and dermatome, can the nerve conduction test be used to localize the site of the nerve problem? I mean can it tell the distance of the pathology compressing on the nerve from the skin surface?

hello I have a liquid or gas inside a metallic box (eg. stainless steel 5mm thick) how can I increase its temperature without heat convection or conduction?

Homework Statement Rods of copper, brass and steel are welded together to form a Y-shaped figure. The cross-sectional area of each rod is 2.0 cm2 . The free end of the copper rod is maintained at 100◦C, and the free ends of the brass and steel rods at 0 ◦C. Assume there is no heat loss from the...

What's the electric field strength needed to get one of lithium's core electrons into the conduction band? How do you figure this out?

Hi, I shall be grateful if someone can throw light on the heat transfer processes taking place through in this very simple example. Consider the attached image (pdf). See figure (c) which I have also marked in red block. It is pot lying on a hot plate. I want to know the heat transfer...

Hi all, I am not sure if the is the right place to post the question being new to the forum, but I am looking for some help with a heat transfer experiment that I ran for my honours thesis. Essentially the aim is to determine if warmed saline fluid bags taped to 3 different types of tree barks...

I read in a book "Optoelectronic Integration: Physics, Technology and Applications" edited by Osamu Wada. Ballistic Conduction and Superconductivity are both electron transport that are not affected by the collisions and scatterings. Ballistic conduction or Ballistic transport occurs when the...

Ballistic conduction occurs when the length of the conductor is smaller than the mean free path of the electron. Ballistic conduction differs from superconductivity due to the absence of the Meissner effect in the material. A ballistic conductor would stop conducting if the driving force is...

When a body is postively charged q and another uncharged body is touched to it what happens to both the bodies...why and how is charge distribution...please explain

It seems like when an electron moves to a higher energy level, even within the same band (conduction), the empty state should be a hole. But, we are told that in metals, electrons are the charge carriers. Do I just misunderstand what holes are? Or what is going on here?

Ok, I've built a numerical model to show the cooling of hot magma sills entered into the crust over time. The results show that the volume of the "hot" zone when the emplacement of a constant volume of hot sills is all done will vary as a matter of two things: the overall rate at which the magma...

Homework Statement [/B] Explain how the concept of thermal resistance can be used in the analysis of heat transfer problems 2. The attempt at a solution So I'm made a few key points but I am not sure if I have answered the question fully: Thermal resistance is a heat property and a...

I am modeling the injection of hot magma sills into the Earth's crust at varying rates (and varying sill heights for each rate). For instance, for a total of 16 km of magma ... 1a-n. 40, 400m high sills emplaced at rate of 5e-3 ma-1, 5e-4 ma-1, 1e-2 ma-1, , 2e-2 ma-1, 3e-2 ma-1, and 4e-2...

We Know that in conductive Solids there are lots of free electrons available & they drift when electric field is applied. Their drift velocity is in the range of mm/sec to cm/sec. Now if we consider any conductive liquid which is flowing & we connect the electrodes in such fashion that the flow...

Homework Statement This is a problem regarding transient heat conduction in an undefined semi-infinite solid, initially at a temperature T0 whose surface temperature is suddenly raised to a new constant level at Ts. I also supplied the problem as an attachment for ease in explaining the...

I didn't put this in the Education forum because I feel the level is probably too high. I have a physics degree and an education degree, but due to my inability to tolerate students who simply don't care about learning, I became an electrician instead. My colleagues and I were having a...

Hi, I'm doing a 1D thermal conduction simulation on Comsol Multiphysics 4.4 and my first component is vacuum. I did'nt found the vacuum in the material list. Should I create a new component with a null thermal conductivity ? Thanks

My question is as follows: if you place an insulator into an applied field, the only thing that will happen is that the potential energy of each band will shift, according to the potential that it is in. Why is this exact same thing not what takes place in conductors? Why do the electrons at the...

Aluminum foil reels have to be preheated for manufacturing but it's inefficient (the doors aren't sealed and the material isn't in close contact with heating elements at the sides). I'm considering an initiative of more efficient design. How difficult would it be to evaluate heat transfer if...

Hi Guys, I'm new on this forum, currently studying Aerospace Engineering and am trying to produce the model of a radioisotope thermoelectric generator using numerical methods to solve the heat conduction equation as part of my research. The way it works is that I have a radioisotope source in...

Homework Statement http://postimg.org/image/4ctgrkoop/ I don't understand the final bit, for the 'steady rate of heat transfer for the entire fin', how they went from Fourier's Law to that final expression. Homework EquationsThe Attempt at a Solution I think it involves the previous expression...

Homework Statement Options for answers: positive, negative, neutral, cannot tell 1) a positive point charge is brought near the outside surface of a neutral conducting sphere and released. The initial position of the point charge is on the on the positive x-axis and the sphere is centered on...

Say you have a flat resistor that is producing heat. You place the resistor against a sheet of steel and wait for equilibrium. One side of the steel is now at the same temperature as the resistor (assuming negligible contact resistance), the other free-air side of the steel is at a lower...

What exactly is conduction band?electrons from valence band jump into conduction band where they exactly go ,do they go to higher shell or subshell or orbital or stays in same place with more kinetic energy?

Hello, I just began learning mass transfer, and I am trying to use analogies from heat transfer to help me solve problems. For example, if you have one dimensional heat transfer through a plane wall, I would start with a general energy balance. $$\frac {dE}{dt} = \dot Q_{x} - \dot Q_{x + \Delta...

I am learning the basic make-up of LED's and they mentioned conduction and valence bands. What I am unsure of is which of these bands are either the p-type or n-type materials within the LED/semiconductor, and/or which band is positive with holes or negative with the free electrons. Can I just...

Homework Statement Two bars are placed between plates whose temperatures are Thotand Tcold . The thermal conductivity of bar 1 is six times that of bar 2 (k1 = 6k2), but bar 1 has only one-third the cross-sectional area (A1=1/3 A2 ). Ignore any heat loss through the sides of the bars. Which...

Hi all, I have a unique problem that I need help with A company's curing oven's exposed surface temperature is measured at 80°c when the surrounding air is 23°c. You think it should be insulated and wager to pay for the cost of this yourself if you can keep the savings incurred. Is this a smart...

Homework Statement I am attempting to solve a question which asks the carriers in Ag. Homework EquationsThe Attempt at a Solution Is the use of the word 'Carriers' simply another way of saying excited conduction electrons? Thank you.

For my homework I was given a velocity diagram of the Juan de Fuca plate similar to this: The first question is as follows: Measurements indicate that the Juan de Fuca plate is moving at a speed of ~40 mm/year. Calculate, and draw diagrams that show, the horizontal and vertical components...

When you have energy going through a plane wall, I know that the heat flow rate should be constant, meaning what comes in should go out. But is this true even if it is transient, and a non-steady state process? I think the energy content of the plane will not change for steady state, but for...

Hi, I was provided a http://eng-tips.com/viewthread.cfm?qid=372664# that I'm lost on. I was given an equation that we solved for earlier in the semester using the finite difference (dx method). (first image below). The http://eng-tips.com/viewthread.cfm?qid=372664# wasn't clear when...

Fourier's law of thermal conduction states that \mathbf{j}=-k\nabla T, where \mathbf{j} is the heat flux. Integrating both sides of this equation over a closed surface gives the equation \frac{dQ}{dt}=-k\int \nabla T \cdot d\mathbf A. If there is a temperature discontinuity across this...

Homework Statement Determine the thermal conductivity of a metal (assume linear heat distribution at steady-state, and well insulated), given, Thot = 96.8 Tcold = 29.5 There is also: 13.7 W being pumped in at one end. Water convecting heat away on the other end. Homework Equations...

Hi everyone I am trying to solve non linear heat conduction where thermal conductivity is function of temperature, I am solving it by finite difference method. this is my equation ∂2t/∂x2+∂2t/∂y2 *k(t)= -q (x,y) i have solved the equation taking k(t)= a-b*t,and when i further solved the...

Hi guys,I am new for programming. I made my first attempt to solve an heat equation by finite difference method and wrote a code for it in Matlab.I got a solution but i need help from you guys to (vectorize) increase the speed of my program. ((∂^2 T)/(∂x^2 )+(∂^2 T)/(∂y^2 )+(∂^2 T)/(∂z^2...

When studying about semiconductos what are the valence band and conductivity band .what are its properties,where is it addressed.

Homework Statement In general, a sphere with conductivity ##\kappa##, heat capacity per unit volume ##C## and radius ##R## obeys the differential equation at time t: C\frac{\partial T}{\partial t} = \kappa \frac{\partial^2 T}{\partial r^2} + \frac{2\kappa}{r}\frac{\partial T}{\partial r}...

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...

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...

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...