Conduction Definition and 397 Threads

If I have the equation -k*dT/dr=0 do I get rid of the constant k and integrate, or do i integrate first and keep the constant?

in winter, wooden floor feels cold to the barefoot but the rugs and carpets don not feel cold although the floor and carpet are at the same temperature?

I was given an oven that comprises of several cylinders that fit inside one another. The innermost cylinder is a Molybdenum oven that will hold a sample of metal. A ceramic cylinder fits over this. A tungsten wire heating element is wrapped around this cylinder. Two more ceramic cylinders fit...

Homework Statement For the rod in Problem 10 (already solved this, see below): (a) plot u vs. x for t= 5, 10, 20, 40, 100, and 200 (b) plot u vs. t for x= 10, 20, and 30 (c) how long does it take for the entire rod to cool off to a temp. of no more than 1 degree C? Homework...

Homework Statement Folks, I am self studying through a heat conduction problem involving a 2nd order linear homogenous differential equation which has the solution of the form ##\theta (x)=C_1\cosh mx+ C_2\sinh mx## (1) where ##m \equiv \sqrt \frac{c}{a}= \sqrt{\frac{\beta P}{k A}} ##...

Is anyone here familiar with the speed of a temperature wave through Si02 or other electrical insulators? Thanks, S.L.

My hypothesis is to use two different stable heat sources with different tempreature T1 and T2 (T1>T2) transmits the heat . Then I let the distance between this two heat sourse filled with idea gas or ideal metal in a tube. So if the distance is L, the heat capacity is Cv (Constant). So the...

Conduction in reverse biasing too?? Is it the case with transistor?? I have a mechanical analogy of diode in which a socket is provided with a one way valve. (figure 1st below). The arrow inside the circle shows the direction of motor pump. When there is enough pressure to lift the valve...

I know that Newtons law of cooling is useful when a solid is transferring heat to a fluid. And conduction equation is used in solids. My question is: 1) Can Newtons law of cooling be applied in case of solids (apart from Heat conduction equation)? 2) Can Newtons law of cooling be applied in...

I was reading about electronic band structure in wiki and I didn't understand why the conduction bands are necessary for flowing current in a material. If all the atoms in a solid shares valence band and all its eletrons, then these electrons may travel through the solid. I didn't get why the...

I'm creating a project where I am attempting to melt solder paste using the current running through two copper wires, in a kind of lap joint. I'm trying to figure out how much current would actually be going through the wires if I use a 9V battery. I'm not sure where to take into account heat...

I am confused as to how heat transfer really works. I've read all about conduction/convection/radiation. Radiation makes sense to me, electrons enter a higher band, come back down and give off energy in the form of EM waves. These waves can then be absorbed by other atoms causing electrons to...

Using Fourier’s law and an electrical analogy, derive the expression given below for the heat flow, Q, through a flat composite wall of surface area, A, with three layers of thicknesses x1, x2 and x3 and thermal conductivities k1, k2 and k3, and an overall temperature difference ΔT. State any...

Consider a wire of length l. At time t=0, one end of the wire is at temperature T_0, while the rest of the wire is at temperature T_1, T_1<T_0 (for example, one end of the wire is kept in contact with an external hot body, at temperature T_0). After how much time the temperature near the second...

Conduction - Heat Equation - Units Don't Add Up! Hi there I have what I think/hope is a simple question: I've been working on heat inputs and outputs in inertia friction welds and have managed to produce a net power term (W) as a function of time. I now want to use that in the heat...

Say we have a laterally insulated beam and some boundary conditions at either end, be it convective or fixed-temperature, but the cross-sectional area is variable. If the cross-section were constant I'd just say it were a 1-D problem, but I'd imagine that having the cross-sectional area be a...

I have two questions. I believe I have solved the first question and would like confirmation of this answer; the second question I'm a little bit lost on so any help there would be greatly appreciated! I am working on a problem set in which I must derive the equation for heat conduction in...

Hello Forum, I am looking at the energy levels between the n and p regions of a diode. The p-side has a conduction band that starts at a higher energy (same for the valence band). The n-side has the valence and condution bands that are at lower energy. The Fermi energy line is the same...

Homework Statement Consider unsteady state heat conduction through an infinitely wide slab of solid material of thickness 2L. There is no internal heat generation and the thermal properties of the material are independent of temperature and position. Starting from an energy balance, show...

hello, i have a question related to metallic bonding. As far as i know, valence band is defined as the highest filled level in the band and conductionband as the 1st unfilled level. So, if I have 100 Li, we will have 100 orbitals which form a band. Since we have 100electrones, 50 pairs, so we...

I used to think that the heat does rise even in solid metals with no gas/liquid around (No density argument is possible then.) But couldn't find anything describing or even verifying it. I'am pretty sure the gravitationally induced anharonicity in the atomic core potentials should have at...

Hi and thanks for reading, I don't really understand the valleys in the conduction band, in the E vs. k diagram, there is the L-valley, r-valley and X-valley. Each has a different momentum... and are at different energy levels. I understand that at any temperature above absolute zero, a...

I am doing a zainy experiment at home. I need to devise a way of applying a cooling intensity factor (CIF) of around 70 mW/cm2. I need to cool material that is roughly 30 degrees Celsius down to around 2 degrees Celsius. The cooling has to last for a period of one hour or more. The surface...

In my book I'm reading about heat, specifically convection. There is an image of a person with a drink in their hand, suntanning while a fan blows on them. I get that the drink represents conduction, the sunlight is radiation, but how is the fan convection?

Homework Statement The average rate at which energy is conducted outward through the ground surface in North America is 54 mW/m^2, and the average thermal conductivity of the near-surface rocks is 2.5 W/mK. Assuming a surface temperature of 10 C, find the temperature at a depth of 35 km...

Determine the heat loss through a 1m square pane of 6 mm thick glass for a temperature difference of 15oC. Thermal conductivity of glass is k = 0.72 W m^-1 K^-1 Solution Rate of loss of heat = 0.72W m^-1 K^-1 x 1 m^2 x 15oC/(6x10^-3 m ) <--- Ok so I understand everything but I don't...

Ok, I am looking over stuff for an exam. I am a bit confused on something. When conductivity is zero, a medium is lossless. Zero conductivity means infinite resistance. For infinite resistance, no electrons will flow, but an electric field can propagate forever. A wire has high conductivity, so...

I quote from Oliver Heaviside, "Electromagnetic Theory", 1893, p.15: It was discovered by mathematical reasoning that when an electric current is started in a wire it begins entirely upon its skin, in fact upon the outside of its skin; and that, in consequence, suficiently rapidly...

Hi, I understand for metals the conduction band is usually partially filled. However, at absolute zero, is the conduction band empty (for metals)? I'm asking this because as far as I know, the definition of valence band is "the highest occupied band at absolute zero" However, I have...

how is the relationship between fermi level and band structure of solids can effect electrical conduction properties of a material?

air, glass, mica, rubber, water, etc all are insulators because they don't have free charges to carry the current... I don't understand what do we mean by "carry"?? i mean, i don't really understand what happens at the micro level during electrical conduction through a medium...How do the...

Homework Statement Given is a hollow cilinder with inner radius R1 and outer radius R2. The heat conductivity of the material is k. The cilinder has length l and an inner temperature of T1 and outer temperature T2. Determine the temperature gradient in the cilinder and the heat flow that leaks...

Ok, so let's say I have a simple half-wave rectifier like the one shown in the image below: http://img585.imageshack.us/img585/1904/unledmwc.jpg When it comes to the analysis of the circuit, during the positive cycle of the input voltage, the diode is forward biased and the output voltage...

We know in silicon a valence electron can be excited to conduction band if it absorbs one photon(one photon absorption) or two photon(two photon absorption),my question is that it must need a certain amount of time for the electron to 'travel' from the valence band to the conduction band(I...

Hi, I have written a numerical code to solve the 1D heat equation in cyclindrical coordinates: \frac{\partial T}{\partial t}=\kappa\left(\frac{\partial^{2}T}{\partial r^{2}}+\frac{1}{r}\frac{\partial T}{\partial r}\right) The problem I'm considering is a hollow cylinder in an infinite...

Homework Statement Find the solution of the heat conduction problem: 100Uxx=Ut, 0<x<1, t>0; U(0,t)=0, U(1,t)=0, t>0; U(x,0)=sin(2\pix)-sin(5\pix), 0\leqx\leq1 Homework Equations U(x,t)=\sumcne(-n2\pi2\alpha2t)/L2sin((n\pix)/L)...

Hello, Can anybody explain to me how does this: dQ=-X*dS*grad(T)*dt t being time and T being TD temperature. transforms into this: Q=-X*S*(T2-T1)*delta(t)/d delta(t) being time interval d being thickness length of material X being heat conductivity Thanks

Homework Statement Electrons present in the outermost orbit are valence electrons. If we supply sufficient energy to these electrons they make their transition from valence band to conduction band and electrons in conduction band are termed as conduction electrons. My question is, take for...

Homework Statement For copper we find that J=\sigmaE , where \sigma has the value 5.8x10^7 mksc units. If an alternating electric field represented by E0ei\omegat exists within the copper. Find the ratio of the conduction to the displacement current density at a frequency of 1megacycle/sec...

In Bird, Stewart, Lightfoot "Transport Phenomena", they post the following equation for heat conduction with a nuclear heat source: Sn=Sn0 [1+b(r/R)^2] where Sn is volumetric thermal energy, r is radius and R is radius of the fuel pellet. The text state that b is a dimensionless...

1. The problem statement I'd like to use Matlab to help me model and solve a simple 2D steady state heat conduction problem: A square section duct is buried in the Earth some distance below the surface. This duct is at a steady temperature of 60 degrees C. I need to use the central divided...

1. A large block of steel [k=45 W/m°C, alpha=1.4x10^-5 m2/s] is initially at a uniform temperature of 35 C. The surface is suddenly exposed to a constant heat flux of 3.2x10^5 W/m2 Find the temperature at a depth of 2.5 cm after 30 seconds has elapsed.

I need to calculate the density of states for a dispersion relation which is like the free electron dispersion, but with one effective mass in the kx, ky directions, and a different effective mass in kz. So I need to integrate the inverse gradient of E(k) over a surface of constant energy, ie...

Warning: I'm not a practicing chemist. Answers in as-simple-as-possible language (but not oversimplified!) would be greatly appreciated! I'd like to know if the chemical properties of a solid can be affected by conduction band electrons. I assume that, in the majority of cases (and perhaps...

Homework Statement There's a slab of a material with temperature T1 on the left and the T2 on the right. The thickness of the material is l with area A. In the centre, there is heat generation Qvol in the centre, which is a thin rod. Find the heat transfer Q through the material. Homework...

Hi everyone, I recently started studying heat conduction using differential equations and this has been stumping me for a while. I am having trouble understanding what type of heat conduction problem this is. We are given a 100cm long copper rod with ends maintained at 0 C. The center of the...

Homework Statement Let the ends of a copper rod 100 cm long be maintained at 0 degrees C. Suppose that the center of the bar is heated to 100 degrees C by an external heat source and that this situation is maintained until a steady state results. Find this steady-state temperature...

Homework Statement I am trying to find the temperature profile through a cylinder wall. It is a one dimensional, steady state conduction problem without internal heat generation Homework Equations d/dr(r*dT/dr)=0 where r is radius and T is temperature The Attempt at a Solution I...

When stimulated in the middle of axon, nerve conduction is bidirectioal. Now I know the andromic conduction stops at the first synapse. Is the reason for this, that there are no neurotransmitters in the body of a neuron, and more importantly no calcium channels there to activte them. Thanks :smile:

Homework Statement The following cylinder has a temperature inside Ti and temperature outside To. Using the general equation for heat conduction in a cylinder, write the temperature distribution equation as a function of the radius T(r). What is the temperature midway at r=a? (Take the heat...