Conduction Definition and 423 Threads

Students seeking “deeper” understanding of basic electricity, frequently come with one of the following misconceptions. 1. Electrons are like balls, they start with potential energy and gain kinetic energy. They deliver their energy to the far end of the wire by filling a bucket. 2...

Okay...Is it possible to charge a metal, by conduction, using only a single terminal of a battery?...Like it we touch only the negative terminal with the metal, is it going to get a negative charge??...If not, then why?

Homework Statement Homework EquationsThe Attempt at a Solution The probability of getting a state with energy ## E_v## is ## \frac { N_v } { N_v +N_c } = \frac1{ e^{-(E_v – E_f)/k_BT} +1} ## ………….(1) Since, ## E_v < E_f, e^{-(E_v – E_f)/k_BT}>>1 ## as ## E_f – E_v>> k_BT ##……….(2) So...

Homework Statement The question below is asking how long it would take for the cooler side of the handle to heat up till its unbearably hot. I'm having a bit of trouble trying to understand the solution and would like some guidance. I can't seem to get how the ##\Delta T ## that represents...

Homework Statement How many free electrons are there in the CB? Diamond has a bandgap of ##5.5##eV.Assume the material is at room temperature and that there are ##2 \times 10^{22}## cm##^{-3}## electrons in the material. What does this mean for their use in semiconductor devices? Homework...

Homework Statement Question C(ii) Homework Equations dQ/dt =-kA(dθ/dx) dQ/dt = (θ1-θ2)/ ((lx/kxAx)+ (ly/kyAy)) The Attempt at a Solution So the first time I tried at this question, I was using the second equation provided above,but when I check the answer, they put the area on the numerator...

Homework Statement I am trying to prove that the diode conducts between the expressions shown here: Homework Equations I know that Vo = Vpsin(wt) and the only information i know about the diode is it has a turn on voltage of Von. The Attempt at a Solution I have tried to plug the variables...

Hello Everyone, Could anyone please explain the difference between the conduction current density (J=σE) and the convection current density (J=ρvd)? I really appreciate any examples or applications to further elaborate these two theories. Note: vd is the particles' average drift velocity...

Hi I am trying to do a transient heat transfer calculation. The water flowing through the pipe is laminar (1 m/s, id = 0.0127 m, Re_d = 0.01) transferring heat to the pipe via convection, then the pipe (od = 0.015875 m, l = 144 m) transfers heat to the ground again via conduction. I found this...

Homework Statement Homework Equations dQ/dt = -kA(dT/dx) The Attempt at a Solution I tried to use Fourier's law of Conduction on this one. I subbed dT for (Θ0 - Θ1), and l(t) (function for thickness of ice against time) for dx, reason being that the sheet of ice should get thicker. I then...

Homework Statement Homework EquationsThe Attempt at a Solution Part 1.1) I managed to find the energy needed to melt the ice, before using ΔU = Nf½KΔT to solve for the new temperature, which was correct Part 1.2) Initially tried using ΔQ = mcΔT before realising that I didn't have the mass...

Homework Statement Consider the slab shown in Fig. 18-18. Suppose that L 25.0 cm, A 90.0 cm2, and the material is copper. If TH 125 C, TC 10.0 C, and a steady state is reached, find the conduction rate through the slab. Homework Equations Pcond = Kc *A*(TH - TC)/L K = 401 W/m*k The Attempt at...

Homework Statement This isn't a homework question but something I'm working on that I thought should be simple. Two disks (area ##A## and thickness ##d##) are joined together and placed under a radiation heater in vacuum, so that one side of the top disk is heated with a constant power. Assume...

Hi all, I am currently considering a heat transfer problem. In this problem a rectangular vessel made of stainless steel is heated by a surrounding jacket with hot combustion flue gases flowing through it. This means that the heating of the rectangular vessel is achieved primarily through...

My friend and I were planning on possibly developing our own tobacco vaporizer, but we lack the electrical engineering knowledge. We know they are simple devices with few parts, (a battery usually being the largest one) and we just were not sure how exactly the electrical energy was transferred...

Can someone tell me if my logic is correct here. I am trying to figure out how the cross sectional area to make the heat transfer from one object be the maximum amount of heat transfer with the minimal amount of area... I know the thermal transfer coefficient is watts per (meter*kelvin). I find...

Homework Statement The door of a refrigerator is 1.5 m high, 0.80 m wide and 6.0 cm thick. Its thermal conductivity is 0.21Wm-1 degrees Celsius-1. a) what is the heat loss per hour through the door neglecting convection effects? b) Air is usually still inside the refrigerator so there will be a...

1. Homework Statement I've been failing to find examples dealing with "longitudinal" thermal conductivity and how two objects in contact with each other would affect the heat flow compared to not being in contact at all. Problem: Given the following information, determine the thermal energy...

Okay...It is written so often, even in the kinetic molecular model, that molecules of a substance (or atoms) collide with each other...so what does the collision of an atom actually mean, like at an atomic level...Do atoms get close to each other so that their electrons repel each other?...Also...

How do I relate Fourier's Law of Heat Conduction for 1-D Heat Conduction with the Heat Conduction Equation in a large plane wall and energy balance equation? Fourier Energy Balance energy in - energy out = system energy change rate of energy in - rate of energy out = rate of system energy...

Homework Statement An infinitely long cylindrical shell has an inner radius a and outer radius b. If the inside is maintained at a temperature Ta and the outside at a temperature Tb, determine the rate of heat flow per unit length between inner and outer surfaces assuming the shell has a...

Homework Statement I have one dimensional heating system. In the center is heating source which is heating two PVC elements located on both sides of the heating source. Heat distribution in other dimensions is negligible because of insulation. Thickness of one PVC element is 0,051 m and surface...

I have designed a gangway for a schoolproject, the gangway made in 2 parts the second part can retract in the first part. The total length is 35 meters, I'm looking for aan good way to make the two parts go smooth in an out eacht other. I was looking into Teflon and what i thought it was a...

Hello, Im having some issues with my task. 1. Homework Statement The heat generation rate of a cylindrical fuel (D=0.2 m and 1 m long) is 160 kW. The thermal conductivity of the fuel is 100 W/mK and its surface temperature is maintained at 283 K. Determine the temperature at the axis...

Hi, Does anyone know if there are such characteristics that are tell tale signs of diode degradation? I'm not sure if diodes fail short or open, I'd have thought open, but I'm not sure. I was wondering if as a diode gets old the forward bias voltage might increase? Or the diode power loss per...

Homework Statement The figure shows wire section 1 of diameter 4R and wire section 2 of diameter 2R, connected by a tapered section. The wire is copper and carries a current. Assume that the current is uniformly distributed across any cross-sectional area through the wire's width. The electric...

The problem: A simple cubic metal has an electron density such that the Fermi energy just touches the edge of the first Brillouin zone. Calculate the number of conduction electrons per atom for this condition to be fulfilled. The attempt at a solution: I know that the electron density for a...

Homework Statement In order to stay warm, divers often wear some sort of thermal protection, like a "wetsuit". Often this is a neoprene "foamed" material, which traps gas bubbles as the insulating material. For this problem, assume: the thermal conductivity is that of air (κ = 0.03 W/m-K) the...

I am studying introduction to solid state physics and it's stated that when germanium is n doped energy states with energy -0.1 ev are introduced, then it's stated that this means that the donor level is 0.1 ev below the Conduction level Does that mean that the Ec is considered 0??

I’m working on an experiment and would appreciate some guidance to characterize the performance of it. I have a small homemade copper coil submerged in a 3 gallon water tank. I’m delivering hot water to the coil that in turn heats the water in the tank. I sense I’m looking for a rate of heat...

Homework Statement Homework Equations power loss = I2R power loss = V2/R The Attempt at a Solution voltage across diode is 0.7V, current is 100A. resistance = 0.01 ohm. Power loss is I2R - 100 * 100 * 0.01 = 100 W Power loss across IGBT = V2/R. V across IGBT = V across Diode = 0.7. R for...

Hi, everyone! I'm doing a research in gap conduction calculation models in popular nuclear fuel performance codes. I want to make a sensitive analysis in their behaviors, but unfortunately, I just have access to FRAPCON package. is there anyone who can help me to gather some of the codes...

Homework Statement so, i had this question where i had a sphere and a cylinder with given dimensions and propreties ( roh, C and k) he also gave me initial temperatures, then both of them dipped in a bath of water of given temperature but unknown h ( convective coefficient) then he gave me the...

Homework Statement Problem data:[/B] http://imgur.com/a/hEz16 Homework Equations Rconduction=ln(rout/rin)/2*pi*Length*thermal conduct Rconvection=1/2*pi*Length*routside*convective heat transfer outside =>Qconduct=2*pi*Length*thermal conduct*(Tin-Tout)/ln(rout/rin)...

Are metals better conductors in the presence of visible light? Considering photons in visible spectrum are not energetic enough to induce emission from a metal surface but they do cause the ejection of 'conduction electrons' which are bound to the metal by a few electron volts.

Hello, I am an electrical engineer rather than a physicist, however, I am trying to understand the physics of a twin wire transmission line in terms of the charge and current density. Let's say we have a lossless, infinite length, twin wire transmission line, a step current is induced into the...

Hello! In order to obtain the number of actual electrons in the conduction band or in a range of energies, two functions are needed: 1) the density of states for electrons in conduction band, that is the function g_c(E); 2) the Fermi probability distribution f(E) for the material at its...

Homework Statement This is the question as it was given...no other data was given. Obtain Fourier's heat conduction equation in three dimensions in an infinite medium in steady state.What modifications will be required in case of a finite body? 2. The attempt at a solution Well I can derive 3D...

Homework Statement We previously solved the heat conduction problem in a ring of radius a, and the solution is c into the sum, perform the sum first (which is just a geometric series), and obtain the general solution, which should only involve one integral in ϑHomework Equations...

Homework Statement Suppose we have a lake and a layer of ice on top such that the bottom of the lake is maintained at a constant temperature T_{bot} which is above the freezing point of water, and top of the ice is maintained at the air temperature T_{air} which is below the freezing point of...

A hot object in thermal contact with a cold one will finally reach a temperature in between. Why can the entropy change of each object be calculated as if the process was reversible? Is there a reversible process with the same final and initial state and what would that be?

If the temperature of the wall is homogeneous i.e. the entire wall has the same temperature: T1 being the temperature of the left wall and T2 being the temp of the right wall, how will heat transfer take place? Can convection occur here? If yes then how will the bulk motion be set up? I am...

Usually it is said that loss of heat through a chunk of material because of conduction is proportional to difference in temperature and inversely proportional to thickness of material. E.g. if I got a wall to ΔQ = K*S*ΔT/D. where ΔQ - is energy flow through material. K - constant characteristic...

I am not sure I quite understand the distinction between the valence and conduction bands in metals. The simple model we learned in Intro to Chemistry explained that electrons in the metals were delocalized and were shared between all the metal atoms in the metallic crystal. I am not sure if I...

In my physiology (biological science) class it was explained that, upon eating some food source, some energy is converted into a useful form for the body, and some energy is lost in the form of heat. The lecturer didn't explain what form this heat is in. I thought that 'heat' must be an EM...

Homework Statement A conduction electron moves through a block of Cu until it reaches the surface. At the surface the electron feels a strong force exerted by the nonuniform charge distribution in that region. This force tends to attract the electron back into the metal which is what causes the...

Homework Statement A very long cylinder has temperature T1 impressed on half of its peripheral surface and temperature T2 impressed on the other half. Find T(r, θ).Homework Equations governing eq 1/r ∂/∂r(r∂/∂r)+∂2T/∂z2 The Attempt at a Solution I am right at r=0 ;T=T1 at r=r' T=T2 to make BC...

A typical example is a iron chair gets cold in winters and wooden chain not. We all know iron is more conductive but how this thing possible at molecular level of conduction of heat from metal to air. In general conduction I know it is possible due to vibration transfer of molecules but how it's...

Just wondering if there are substances (even just theoretical ones) able to conduct heat without heating up itself. How does that operate? What properties are different from that of ordinary substances?

Considering one dimensional heat conduction we may write the Fourier's law of heat conduction in the x-direction as, ##\dot{Q}_{x}=-kA\Big(\frac{∂T} {∂x}\Big)## where, ##\frac{∂T} {∂x}## is the temperature gradient which is basically the slope of the temperature curve on a T-x diagram...