# What is Conductivity: Definition and 403 Discussions

The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by

k

{\displaystyle k}
,

λ

{\displaystyle \lambda }
, or

κ

{\displaystyle \kappa }
.
Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials like Styrofoam. Correspondingly, materials of high thermal conductivity are widely used in heat sink applications, and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is called thermal resistivity.
The defining equation for thermal conductivity is

q

=

k

T

{\displaystyle \mathbf {q} =-k\nabla T}
, where

q

{\displaystyle \mathbf {q} }
is the heat flux,

k

{\displaystyle k}
is the thermal conductivity, and

T

{\displaystyle \nabla T}
is the temperature gradient. This is known as Fourier's Law for heat conduction. Although commonly expressed as a scalar, the most general form of thermal conductivity is a second-rank tensor. However, the tensorial description only becomes necessary in materials which are anisotropic.

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1. ### Rank Copper, Brass and Bronze by Thermal Conductivity

Hi, Can I get help ranking Copper, Brass and Bronze by Thermal Conductivity? This stuff below says Copper is the best Thermal Conductor, and Bronze is the worst. https://en.wikipedia.org/wiki/List_of_thermal_conductivities https://www.engineersedge.com/properties_of_metals.htm...
2. ### Does Heating a Metal Wire Change Its Properties?

I have attached a PDF file.
3. ### Saltwater Pool/lightning Scenario for computer game

TL;DR Summary: What would happen if a bolt of continuous lightning hit an enclosed saltwater space with someone swimming far below the surface? Hello! I'm actually asking this as a DM for a DnD campaign. One of my players trapped a bad guy within a large (30m/side) freestanding cube of...
4. ### I Do valence electrons determine electrical conductivity?

I have trouble researching whether valence-electrons take part in electrical conductivity. Some sources say that a lower amount of valence electrons lead to an higher electrical conductivity, whilst others say the opposite. And each have their different reasons, for example, lower valence...
5. ### Measuring thermal conductivity of a metal

What'd be practical method and/or portable, simple tool (like sort of electricians' multimeter) to meter the heat conductive constant of a metal?
6. ### Low Heat/Thermal Conductivity Electric Conductive Materials

What is/are the electric conductive material(s) which has/have the least heat/thermal conductive?
7. ### Electrical conductivity has an effect while charging by conduction?

I understand that electrical conductivity is a measure of how easily charges are able to move in an object. During charging by conduction (for conductors), it seems that we simply have to add the charges of both object together and divide by two to obtain the resultant charge of either object...
8. ### Calculate Conductivity Temperature Dependence in Semiconductors

I have to plot the conductivity dependence of temperature and I have problems with obtaining the right dependency of \mu and n. But let's focus only on carrier concentration first. For n I used the third equation. From what I understand N_D is a constant. I want my plot to look like this: But...
9. ### Quick question about Aluminum Nitride's conductivity

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10. ### B How does heat conductivity work? Al -> Cu

One has two same volume blocks of metal, one Aluminium and one copper pushed together. If the Aluminium is instantly heated to 100 degrees C, since it has significantly higher heat conductivity will the copper draw the heat out and at some point be hotter then the aluminium? Or will it just draw...
11. ### Conductivity and Electric Field relationship

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12. ### I Can Spider Silk Conduct Electricity?

I would like to know if spider's web is conductive. A google search was inconclusive, some sites say that it is conductive, some that it has a high breakdown voltage. The reason I am asking this is that it seems that I got spiders in my room (honestly I don't know where they are coming from)...
13. ### Calculating Effective Coefficient of Thermal Conductivity

I know k is thermal conductivity but my teacher never told me about effective coefficient of thermal conductivity. I tried googling and found: $$k_{effective}=\frac{\Sigma{k.A}}{\Sigma A}$$ But I don't know the area to used that information. Is there another approach to do this question? Thanks
14. ### Thin disc with high thermal conductivity

I've tried to explicitly solve the Fourier's equation in cylindrical coordinates but I'm getting some messy integrals which cannot be solved analytically. Additionally my instructor said that there's a neat trick for this problem and it's possible to obtain the answer in a rather elementary...
15. ### Physical meaning of thermal conductivity tensor

Good afternoon everyone! I've learned that thermal conductivity has a form of second-rank tensor. As you know, diagonal components of stress tensor mean normal stress and other components mean shear stress and like that do off-diagonal components of thermal conductivity tensor have some special...
16. ### Conductivity of hydrogel with rubber silicone in NMES device

I have a question in regards to a neuromuscular device. Can silicone be combined with hydrogel or the rubber silicone encased in hydrogel to form a wrist watch strap combined with a NMES device. If this is possible how would the hydrogel conduct the NMES device and what is the durability of...
17. ### Increase in conductivity of intrisic germanium with temperature

The intrinsic concentration ##n_i## varies with T as ##n_i^2 = A_0T^3e^{\frac{-E_{G0}} {kT}} ## ---> eq1 The mobility ##\mu## varies as ##T^{-m}## over a temperature range of 100 to 400K. For Germanium, m = 1.66 (2.33) for electrons (holes) as per book. The conductivity is given by ##\sigma =...
18. ### What happens to σ (conductivity) when the permitivity is negative?

We are using the textbook by Jin, "Theory and Comutation of Electromagnetic Fields". In the section on metamaterialshe derives the dispersion relationship. He shows that when ε'= -ε & μ' = μ then the dispersion equation γ =\sqrt{jωμ( jωε +σ )} = α + jβ goes to γ = α = ω \sqrt{μ'ε'}...
19. ### Coefficient of Thermal conductivity

We know that, Conduction Heat Transfer Q = KA(t2-t1)/thickness K is the coefficient of thermal conductivity. If T2 = 1020°C and T1= 22°C also consider we know A and thickness value. K depends on temperature. K varies with temperature. For all the materials we have a tabular data of K for...
20. ### How is the thermal conductivity affected by magnetic field?

Hello, I'm searching for how magnetic field affects the thermal conductivity of the metal (such as steel in solid form). If someone suggests any article about it will be very helpful.
21. ### Calculate the HCl concentration in H2O from the conductivity

Hi y'all, I think this is my first time in the chemistry section of this forum, so thank you in advance for your patience with what is (I'm pretty sure) an elementary question. I've googled around for this a bit, but my last acid chemistry study was in 2002 or so, so the reading I am doing is...
22. ### Electrical RF conductivity of copper oxide

In my search, I have been looking for any data that might explain the RF resistance from 3 to 30 MHz range of the two basic types of copper oxides that form on the outside of bare copper wire. I believe these oxides become semiconductors and have large range of impedances. Due to the nature...
23. ### Constant of thermal conductivity and heat flow in a given time

Here is the Q below I want to see if my values for part b) is okay? This is what I have tried: Any help would be nice! Thanks
24. ### A Skew scattering and its proportional behaviour to conductivity

Hallo guys,Im kinda confused about something and hope you can help me. Let me introduce you to it. we take a look on one Mechanismen to the spin hall effect, skew scattering effect. i just read that you can see this contribution only in the clean Limit. So that's really strange for me cause...
25. ### Changing the k constant in voltage potential equation?

Summary:: What if you were calculating the voltage potential for a dipole, but underwater? I'm making a predictive model (in R programming) for the voltage potential at any point around a dipole. I need to be able to change parameters, one being the k constant. V=( kpcosѲ)/(r^2). Where V is...
26. ### Heat Transfer in Metal Tank: Time to Drop from θ2 to θ1

I'm trying to find a heat transfer equation that includes time. Metal tank, partially filled with liquid. I need to find the time it would take for the temperature on the outside of the tank to drop from θ2 to θ1, given thickness, metal and liquid's properties, and tank dimensions
27. ### Overall Thermal Conductivity of Three different layers

Overall thermal conductivity? for example, there are 3 layers made of different materials, having different thermal conductivities bonded with each other; conductivity of layer 1= k_1 = 1 W/m-K thickness of layer 1= t_1 = 0.004 m conductivity of layer 2= k_2 = 148 W/m-K thickness of layer 2=...
28. ### I Is a Copper Conductor Directional?

Hi, A question has arisen an a hifi forum (sorry) that cables can be directional. I dispute this, as the proposed mechanism is diodes in the crystal structure etc. or the drawing process to crate the strands. Assume that it is 99.9% pure copper (CW004A (was C101)) and forms part of a cable with...
29. ### Why is electrical conductivity denoted by G?

I did search Wikipedia and other science related websites, couldn't find an answer. Let me know if anyone knows the story behind G.
30. ### A Exploring Conductivity in Semi-Metallic Materials

Hi, I would like to know if there is some current conduction with hole in semi metal ? thank you
31. ### Heat capacity vs Thermal conductivity in a LN2 bath

I worked on a lab experiment that was meant to measure heat capacity but left me with some other questions. The students measured the mass of a cup of liquid nitrogen as it boiled off, recording mass vs time. Then they drop a solid object into the bath, one experiment with a small bit iron...
32. ### A Can the electron-electron interaction have an impact on the conductivity?

Can the electron-electron interaction have an impact on the conductivity? Google seems to point out that yes for some 2d materials such as graphene. But what about 3d materials? Intuitively, any lost momentum by an electron would be gained by another electron, so in average, this e-e...
33. ### A The relation between imaginary part of permittivity to conductivity

Hi When I read the following article: http://nopr.niscair.res.in/bitstream/123456789/14183/1/IJPAP%2050%286%29%20405-410.pdf I tried to convert the value of the conductivity for saline in 500 MHz. At the article, they present the conductivity as ε'' = 70. Which ε'' is the imaginary part of...
34. ### Calculate the total resistance by integration using the conductivity equation

(i) Dividing the rod into thicknesses of dx we get discs of area A with lengths=dx so using (****) we have the resistance of a typical disc (between point x' and x'+dx) as: (1) ##R(x'dx)=\frac{dx}{g(x)A}## (ii) Using (1) and (*) and the integrating from a to b of the entire rod we get...
35. ### Enhancing the thermal conductivity of Phase changing materials

A) What are the modern techniques used for enhancing the thermal conductivity of Phase changing materials (PCM) ? B) what are the negative effects (disadvantages) of using old methods of enhancing thermal conductivity of PCM ? ( construct table ) C) what are the different techniques used for...
36. ### Can Anisotropic Materials Have Asymmetric Thermal Conductivity Tensors?

Hi, yesterday a professor of mine told me that if you have a temperature gradient along the x-axsis you could have heat flowing in the y direction. Mathematically it is pretty straightforward to find the thermal conductivity tensor required, but in real life can you name some materials that...
37. ### Thermal Conductivity Problem-- Two Reservoirs

Suppose that a large mixture of ice and water is in thermal contact with a reservoir which contains a large quantity of water and steam. Assume that both the ice/water bath and the water/steam reservoirs are otherwise thermally isolated and at a constant temperature. The only contact between...
38. ### Sophisticated Experiment (Thermal Conductivity of Housing Materials)

Hi everyone, I am currently a third year University Student in the UK and I'm in the midst of doing my dissertation. My dissertation topic (Effective methods of decreasing the thermal Conductivity of Housing Materials) requires that I produce several experiments to test and analyse a certain...
39. ### Refractive Index vs Conductivity

Hello all, I would like to know which of the above two methods used in determining concentration of a solution is more accurate? Thanks, KV
40. ### I Understanding L&L's argument, constant current in a crystal

I'm trying to go through chapter III of the vol.8 of Landau and Lifshitz series. (Fortunately the book is uploaded to the archive.org, I guess it is in the public domain.) At page 87 ( << Archive.org link deleted by the Mentors because of copyright violation >> ), they speak about the Joule...
41. ### Does chromium oxide reduce conductivity in stainless steel?

Does chromium oxide reduce the effectiveness of a faraday cage constructed from stainless steel mesh? I am using mesh that is like insect screen for windows. It will be in moist environment. I appreciate your help!
42. ### Possible error sources in thermal conductivity experiment?

Hello, my name is Stephen Lanford and I am currently working on a Physics II lab. I am solving for the thermal conductivity of four materials (glass, plexiglass, pine, and sheetrock) using data from thermal conductivity experiments. The experiments consist of a steam chamber at 100 C, a block...
43. ### Electrode Polarization and Conductivity

The common mantra is that when measuring conductivity in solutions the electrodes will build up a polarization layer and disturb the measurement, thus a 4 electrode measurement is used and an alternating current impressed up on the outer electrodes, usually around 1000 hz. I have been trying to...
44. ### Converting impedence response to electrical conductivity

Hi, I have a curve, impedance magnitude vs frequency. i would like to convert this curve to electrical conductivity vs time. how can i do that?
45. ### Max Heat Transfer w/ Low Conductivity Brick & Copper

Hello, Just a quick question if I have a let's say a heat source of under a layer of bricks that have a thermal conductivity of 1.6 (W/m/°C.) and on top of the brick a layer of copper with a thermal conductivity of 398 (W/m/°C.). Is my assumption right that since the layer of brick has such a...
46. ### Band diagram, conductivity tensor

Hello! Does anyone have an idea of how can I obtain information from a band diagram about the directions along which the system conducts best and worst ? Thank you in advanced! :)
47. ### Need help to explain the peak of thermal conductivity

Progress This is the experimental data of thermal conductivity of stainless steel 304L at low temperature. The data is calculated with the Fourier's law of thermal conduction. I checked many times in the excel file and I confirmed that there is no mistake in the calculation. The parameters are...
48. ### A Conductivity and Integration over Fermi-Sphere?

Hi, I am reading "An Introduction of Solid State Physics" from Ibach Lüth and don't understand the integration process. They write $$\sigma=\frac{e^2}{8\pi^3 \hbar} \int df_{E}dE \frac{v^2_x(\bf{k})}{v(\bf{k})} \tau(\bf{k}) \delta(E-E_F)$$  = \int_{E=E_F}^{}df_{E}...
49. ### How Can Crystal Symmetry Affect Conductivity Tensor Components?

Hello guys! I have to solve a problem about crystal symmetry, but I am very lost, so I wonder if anyone could guide me. The problem is the following: Using semiclassical transport theory the conductivity tensor can be defined as: σ(k)=e^2·t·v_a(k)·v_b(k) Where e is the electron charge, t...
50. ### B 4 Questions About Lenz's Law Experiment

Hello, I have four questions. As it stands now, I don't have the necessary materials to test this myself, which is how I'd prefer to learn the answer. I still plan on doing this experiment for fun once I can acquire the necessary components. This deals with Lenz's Law. My goal is to maximize...