Conduction Definition and 397 Threads

The other day I was at a football match and I had a cup of tea in a styrofoam cup. The tea was practically boiling - far too hot to drink, but the cup was only warm to the touch. I know that if the tea had been in a china cup or mug it would hve been uncomfortably hot to pick up. Why does the...

My question pertains to mechanisms for heat transfer in an everyday situation. I've put that sentence first (rather than the next one) so that people looking at the post preview wouldn't think I was posting irrelevant threads. In Canada, today is Thanksgiving day. The packaging on my Turkey...

Homework Statement I have a cylinder that's made up of three sections, brass, stainless steel, brass. There's a heat source at the top and a heat sink at the bottom. I know the overall heat transfer coefficient, power supplied to the heater, length, diameter, cross-sectional area of the...

"I pour hot water into a metal container. The inside surface of the container gets hot." It is quite clear the inside surface gets hot due to conduction (criteria of process is satisfied). What i am not so sure about is whether radiation is involved. Theory and some gut instinct tells me...

I am trying to solve an advanced heat transfer problem and I have a 2nd order ODE. I can solve the homogeneous solution easily, but I am having trouble with the non-homogeneous solution.Homework Statement Given a turbine blade and asked to model as a one-dimensional fin, subject to the...

An iron pot filled with boiling water is on top of a stove. The bottom has a surface area of 200 cm2 and a thickness of 2.00 mm. If the bottom has a temperature of 480°C, how much heat flows through it per second? Answer wanted in kJ/s Q/t= (kt)A*(deltaT/d) The thermal conductivity...

Homework Statement Describe how a metal sphere on an insulating stand is charged if a positively-charged rod were to touch the sphere. (This is a 5 mark problem, so at least 5 major points should be included in the answer. I am not sure whether I have fully answered the problem.) Homework...

I am not sure how to approach this problem. If you have a carbon steel pipe that is being heated on one end at a constant temperature of 1500C. Can you figure out how much distance in pipe will it require before it cools to 790C? The thermal conductivity of Carbon steel is 54 W/mk. Another...

Homework Statement A copper bar of thermal conductivity 401 W/(m·K) has one end at 102°C and the other end at 23°C. The length of the bar is 0.10 m and the cross sectional area is 1.0 multiplied by 10-6 m2. (a) What is the rate of heat conduction along the bar? (b) What is the temperature...

Hey. I want to derive the conductivity of graphene. I'm looking for a formula of the sort: J = \frac{e}{\hbar} n \frac{dE}{dk} D(E) \Delta E where \frac{1}{\hbar} \frac{dE}{dk} is the electron velocity, D(E) = \frac{dN}{dE} is the density of states, \Delta E might be the applied voltage...

Why does DCM work the way it does? Because it makes no sense (To me, obviously). Not how it works. Why it works. The intuitive form, to me, would be that a lighter load would mean more time before the loop discharges, (due to tau = L/R) but apparently it's the other way around in a buck...

Let's say we use a very simple model consisting of non-interacting electrons in a 3D infinite square well, perhaps a cube of a single metal crystal. If an electron is in a particular energy state, then its wavefunction is spread across the entire crystal. However, electrons are said to...

Homework Statement Which one of the following statements about heat flow is FALSE? (A) Thermal conduction is due to energy exchange during collisions of atoms or molecules. (B) Thermal convection occurs only in fluids. (C) The rate of heat flow due to thermal radiation is proportional to the...

Homework Statement Two well-insulated slabs, one of steel the other of copper, are in close contact as illustrated. Find the temperature at the interface between the two slabs & also the rate at which heat is transferred across the slabs. Thermal conductivities of steel and copper are...

Hi folks, I am new to PF. First I have to apologize for the following english -- it is not my native language. I have problems in understanding the formation of the conduction and valence bands of solids: For example in III-V compound semiconductors both constituents are sp3 hybridized...

[b]1. Homework Statement [/b the ends of a 20cm long,2cm diameter rod are maintained at 0degrees and 100degrees by immersion in an ice-water bath and boiling water. heat is conducted through the rod at 4.5x10^4J/h. of what material is the rod made? Homework Equations Q/dt=k(A/L)dT The...

ok...Two identical rectangular rods of metal are welded end to end (hot dog to hot dog) with a temperature of 0 Celcius on the left side and a temperature of 100 celcius on the right side. in 2 min 10 joules is conducted at a constant rate from the right side to the left side. How much time...

What is the dissipation due to heat conduction? D = -k \frac{\vec q\cdot\nabla T}{T} where q is the heat flux, k is the coefficient of heat conduction and T is the absolut temperature. What is the physical meaning of this?

Homework Statement Diagram is attached showing part (a) and part (b) Two identical rectangular rods of metal are welded end to end (a), with temperature of T1=0 0C on the left side and a temperature of T2=100 0C on the right hand side. In 2.0 minutes, 10J is conducted at a constant rate...

Homework Statement The one dimensional steady-state heat conduction equation in a medium with constant conductivity (k) with a constant volumetric heat generation in three different coordinate systems (fuel rods in a nuclear power plant) is given as: \frac{d^2 T}{dx^2}=-\frac{\dot{q}}{k}...

Conduction "what if" questions... What is the Biot number (hL/k) is greater than 0.1 and I use the lumped capacitance method for analysis (i.e. there are temperature gradients in the "lump" and I have assumed they are absent). What effect does it have on the result? What is the largest...

Homework Statement A problem with odd harmonics only. Show that the solution of the heat equation du/dt=c2*(d2u)/(dx2), subject to boundary conditions u(0,t)=0 and ux(L,t)=0, and the initial condition u(x,0)=f(x) , is u(x,t)= \sum Bnsin[(\pi/2L)(2n+1)x]e-((c*\pi/2L)*(2n+1))^2 where n...

[b]1. what is the magnitude of the force between two parallel conductors 3.0m long,with currents of 5.0 A and 9.0 A, 20 cm apart? [b]2. Fm = IlBsin~ Fm = qvBsin~

Hi All, from this page: http://en.wikipedia.org/wiki/Saltatory_conduction If at node N1, an AP is generated and then the passive spread initiates another AP at node N2, is there 2 APs existing at the same time? In fact, the second AP is ever initiated before the first has ended. It seems...

is a turbine an example of convention? (because it is a fluid or gas) are vents an example of radiation? are heavy drapes an example of conduction? are window tints an example of radiation? because it is a reflector of heat are white tiles and paint an example of radiation?

turbine-convention? (because it is a fluid or gas) vents-radiation? heavy drapes-conduction? window tints-radiation? because it is a reflector of heat white tiles/paint-radiation?

Homework Statement Suppose the insulating qualities of the wall of a house come mainly from a 4.0-in. layer of brick and an R-19 layer of insulation, as shown in the figure. What is the total rate of heat loss through such a wall, if its total area is 190ft^2 and the temperature difference...

I’ve been trying to understand salutatory conduction in myelinated axons and want a better understanding of how depolarization at one node of Ravier causes an action potential at the next. Is it caused by the actual mechanical movement of sodium ions through the axon? There is an animated...

we know that at temperature above 0K, in semiconductor some electron collecting sufficient energy fron surroundings to cross the band gap, placed in the conduction band. But what's the actual procedure to make the transition. I mean to say is it direct absorption of IR photons or by some other...

Here's the issue I'm trying to wade through: 1. If you excite electrons from valence band to conduction band (with a laser say), you are out of thermodynamic equilibrium. In some recombination time, the system will go back to equilibrium. All well in good. 2. Now let us consider a very...

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...

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!

I have to solve a problem regarding "2D steady state heat conduction problem with an internal heat generation source". For boundary value, dirichlet is applied at 3 sides and neumann is at one side. I can solve this problem when no internal heat source exists and only dirichlet is applied...

Homework Statement Since the problem involved formulas I have posted it as an attachment. Please check the attachment first. (I have not scanned this problem, just wrote it in word and posted it) The Attempt at a Solution My approach on this problem is to start with separation of variables...

Hello everyone, new guy here. I'd like some other minds on an on-going debate i have with quite a few people. The subject is "Radiant Floor Heat". I'm not going to cover any formulas at this point as i need to convey the conceptual side of things first. We know that heat is transferred...

This is part of a longer problem, and probably obvious, but if I calculate this wrong, the rest of the calculations will be wrong too!... Question: Given the mass density, molar mass, and electrical resistivity of a substance at room temperature, how do you calculate the concentration of the...

Homework Statement 12.5A, 3.1x10^-5 Homework Equations How far from a long conductor passing a current of 12.5A is the magentic field of strength 3.1x10^-5T? The Attempt at a Solution B= uI/2(pi)r r=uI/2(pi)B =(4pi)(12.5A)/ 2(pi)(3.1x10^-5T) = 8.1x10^5m

Homework Statement the problem is one of understanding. if heat is incident on a surface raising the temperature to some number then conducts through the solid to the other side how much heat energy is actually at the other side?? i understand the temperatures will be different and that heat...

Hi, I understand what make metal a conductor of electricity, but what allows it to conduct heat? Is it that it does not absorb heat because it's electrons are easily liberated?

Hi everyone, From this website (link: http://hyperphysics.phy-astr.gsu.edu/HBASE/solids/fermi3.html#c1 ), we get the following expression: Population Density of Conduction Electron = \int ^{\infty}_{Egap}N(E)d(E) = \frac{2^{5/2}(m \pi k T)^{3/2} exp (-E gap/2kT)}{h^3} My questions are based...

Here is a question I have been pondering on for a while and got rather stuck, could anyone help out? 'A charge is diestributed uniformley with density \sigma over the surface of a hollow conducting sphere of radius a. Show by direct integration that the potential at any point inside it is...

If a wooden cylinder at 298K with perfectly insulated sides (other than the one in contact with the hot plate) where placed with one end on a hot plate until any point on the cylinder reached a temperature of 523K and the power of the hot plate is known and it all goes into the wood. How long...

If heat is applied to one side of a cube, how can the temperature at different distances into the cube be calculated after different amounts of time have elapsed?

Homework Statement Each end of a metal wire is in thermal contact with a different heat reservoir. Reservoir 1 is at a temperature of 752 K, and reservoir 2 is at a temperature of 345 K. Compute the total change in entropy that occurs from the condustion of 1096 J of heat through the wire...

Homework Statement My problem is not necessarily the 2D problem, it's getting the answer in one dimension (I have the y-direction). The problem is the boundary conditions...anyways. Solve for the temperature of a 1D transient metal bar, with the following boundary conditions. Imposed...

Homework Statement Due to its spin, the electron possesses a magnetic moment μB. Treating the conduction electrons in a metal as a free electron gas, obtain an expression for the magnetization due to the magnetic moments of the conduction electrons, when placed in a magnetic field. Evaluate...

I have come across a problem where I must find the rate of heat flow to the surface of a sphere from the center. The sphere has a constant coefficient of thermal conduction. The problem also supplies the temperature difference between the center/surface and the radius of the sphere. My...

Hey everyone! I am currently on a project building a small CanSat. This is a small satellite of the size of a coke can which will be launched together with a balloon and then descend from an altitude of 35 000 m. My problem now is to work out the heat conduction to see if our insulation is...

Homework Statement A large styrofoam cooler has a surface area of 1.0m^2 and a thickness of 2.5cm. If 5.0kg of ice at 0C is stored inside and the outside temperature is a constant 35C, how long does it take for all the ice to melt? (Consider conduction only) Homework Equations...

As I remember learning in school, heat cannot flow from cold to hot. But isn't that true only for conduction and convection? Radiation heat is purely Infrared waves, and there should not be any issue with that. Please correct if I am wrong.