 # Thermal Conductivity of Copper

## What Do You Mean By Thermal Conductivity?

In order to understand the term thermal conductivity, we need to understand first, what conductivity. Thermal conductivity of a material we mean, the measure of its ability to conduct heat. It is commonly denoted by k or λ.

The defining equation for thermal conductivity q = -k⛛T, where q is the heat flux, k is the thermal conductivity, and ⛛T is the temperature gradient which is known as Fourier's Law for heat conduction. It is commonly expressed as a scalar, the most general form of thermal conductivity is a second-rank tensor. In spite of that, the tensorial description only becomes necessary in materials that are anisotropic.

### What Do You Mean By The Thermal Conductivity Of Copper?

The thermal conductivity of copper is the measure of its ability to conduct heat, it means the transfer of heat from one body to another, the thermal conductivity of a substance, k, is an intensive property(a property of a material that does not depend on the amount or shape of the material, a property of the material at a specific point in space.) that indicates its ability to conduct heat. It is often measured with laser flash analysis. Alternative measurements are also established. Due to the composition, mixtures may have variable thermal conductivities. Note that for gases in usual conditions, heat transfer by advection (caused by convection or turbulence for instance) is the dominant mechanism compared to conduction.

If we see the thermal conductivity of pure copper, it is about 400 watts per meter kelvin. This implies that a plate of copper with area A and thickness L whose faces are kept at a constant relative temperature difference of ΔT kelvin will conduct heat at a rate of 400⋅A/L⋅ΔT joules per second. For manufacturing conductive appliances in the United States, copper is the most commonly used metal. It has a high melting point and a moderate corrosion rate. It is also a very effective metal for minimizing energy loss during heat transfer. Appliances like metal pans, hot water pipes, and car radiators utilize the conductive properties of copper.

A variety of options are available to measure thermal conductivity, each of them is suitable for a limited range of materials, depending on the thermal properties and temperature.  By thermal conduction, we mean that it is the transfer of heat from one part of a body to another with which it is in contact and thermal conductivity is a measure of the ability of a material to conduct heat, often denoted by k, λ, or к. Heat transferred depends upon the magnitude of the temperature gradient and the specific thermal characteristics of the material.

### Different Methods To Test Out The Thermal Conductivity Of Copper: -

• Steady-state Method: - In General, steady-state techniques perform a measurement when the temperature of the material measured does not change with time. Therefore the signal analysis is straightforward (steady-state implies constant signals). The only downside is that a well-engineered experimental setup is usually needed.

• Transient Methods: - In this method measurement of thermal conductivity is done during the process of heating up. Therefore the measurements can be made quickly, which is an advantage. They are usually carried out by needle probes.

As copper allows heat to pass through it quickly, therefore it is used in many applications where quick heat transfer is important. These include:

## Applications of Thermal Conductivity of Copper

 Device Use Copper plate Saucepan bottoms Copper pipes Heat exchangers in hot water tanks, underfloor heating system, all-weather  football pitches, and car weather Heat sinks Computers, disk drives, TV sets

### Did You Know?

1. In copper metals, copper atoms are closely packed together.

2. Every copper atom loses one electron and becomes a positive ion which defines that copper is a lattice of positive copper ions with free electrons moving between them. (The electrons are a bit like the particles of a gas that is free to move within the surfaces of the wire).

3. Since the electrons can move freely through the metal, therefore they are known as free electrons. Free electrons also help copper to be a good conductor of heat and electricity, therefore they are also known as conduction electrons.

4. The copper ions  vibrate (see Figure 1). Notice that they vibrate around the same place whereas the electrons can move through the lattice. This is very important when we connect the wire to a cell.

Figure 1 – A section of copper wire showing lattice of copper ions. There are also

free electrons that move through this lattice, like a gas.

1. Copper word is derived from the Latin word ‘cuprum’, which means ‘ore of Cyprus’. That is we use the chemical symbol for copper as Cu.