Conduction Definition and 397 Threads

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...

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

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...

why does diode breakdown into conduction when reverse biased?

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...

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...

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...

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...

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...

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?

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...

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...

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 ...

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?

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?

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...

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...

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...

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...

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

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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!

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...

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...

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...

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...

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...

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?

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...

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

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...

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

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...

We know, heat transfer in a material happens due to vibration or vigorous to and fro movement of particles. Also, the density of wood is much more less than the density of iron i.e, distance between particles is more. Thus, particles in wood has more space to vibrate vigorously than the...

Recently there was a discussion concerning whether an electron in the conduction band was localized or delocalized. The back and forth arguments seemed inconclusive, difficult to follow (too brief too couched in jargon/unrealistic models) and ended in something close to insults back and forth...

Homework Statement A semi-infinite bar (0 < x < 1) with unit thermal conductivity is fully insulated at x = 0, and is constantly heated at x = 1 over such a narrow interval that the heating may be represented by a delta function: \frac{\partial U}{\partial t}=\frac{\partial^2 U}{\partial...

Hello.. The query is regarding thermal conduction of heat from a solid body: Suppose we have a long metallic rod which is insulated on the curved surface and one of the bases. If we supply Q amount of Heat for a small time to the rod from the non-insulated end, initially the temperature of...

Hey all, not sure if this is where I'm supposed to post this question, but it is all about heat transfer. So this is part of my design project for my 4th year of chemical engineering. Problem Statement: A hollow cylinder 400 m long has hot combustion gases T = 500 Celsius flowing through...

Homework Statement A small pond has a layer of ice 1cm thick floating on its surface. The air temperature is -10 C. Steps (a-c) should help you fi nd the final answers in (d) and (e) (a) What is the temperature of the liquid water just below the ice? (b) Write the expression for...

One can show that mass diffusion without chemical reactions obeys the same basic equation as heat conduction. The one dimensional equation in dimensionless variables is given by $$ D_{AB}\frac{\partial^2 C_A}{\partial x^2} = \frac{\partial C_A}{\partial t} $$ where C_A is the concentration...

Homework Statement An insulated spherical conductor of radius R1 carries a charge Q. A second conducting sphere of radius R2 and initially uncharged is then connected to the first by a long conducting wire. (a) After the connection, what can you say about the electric potential of each...