How does cross section affect thermal conductivity?
A: Owing to the fact that the number of collisions increases with increasing area, heat conduction depends on the cross-sectional area A. If you touch a cold wall with your palm, your hand cools faster than if you just touch it with your fingertip.
Is graphite a good thermal conductor?
Graphite is used in pencils and lubricants. It is a good conductor of heat and electricity. Its high conductivity makes it useful in electronic products such as electrodes, batteries, and solar panels.
Why does graphite have high thermal conductivity?
Graphite films, which are currently used for heat dissipation and spreading in mobile phones and other power devices, have a thermal conductivity of up to 1950W/mK. The high thermal conductivity is a result of large grain size, high flatness and a weak interlayer binding energy between the layers.
Why graphite is a good conductor of heat and electricity?
graphite is a good conductor of heat and electricity because in graphite each carbon atom has a free electron in its valance shell,free electron are responsible for conductivity of electricity.
What is the electrical conductivity of graphene?
Most polymers have a low conductivity of about 10−10 S/m, while the conductivity of graphene can be as high as 104–105 S/m [18].
What affects thermal conductivity of a material?
The thermal conductivity of a specific material is highly dependent on a number of factors. These include the temperature gradient, the properties of the material, and the path length that the heat follows.
What are the factors affecting thermal conductivity of material?
Temperature, moisture content, and density are the most important factors. Other factors include thickness, air velocity, pressing, and aging time. The relationship between main factors with thermal conductivity is presented. Uncertainty about thermal conductivity of insulation materials commonly used.
Why graphite is a poor conductor at high temperatures?
Graphite is an allotrope of carbon. It has the properties of bot metals and non-metals. At higher temperature, graphite has an intermolecular structure with immobile ions. Thus, this makes graphite a poor conductor.
Why graphite is a good conductor of electricity and heat?
Why is graphite a good conductor of electricity?
In a graphite molecule, one valence electron of each carbon atom remains free. Due to the free electrons in its framework, graphite can perform electricity. Therefore, graphite is said to be a good conductor of electricity.
Is graphite a thermal insulator?
In graphite, since pi-electrons are free to move throughout the entire layers so graphite is a good conductor of electricity. because of these free electrons it is heat conductor.
How is the thermal conductivity of graphite related to temperature?
The thermal conductivity in the c direction is approximately 2.0 W/m.K and, in that direction, graphite is a good. thermal insulator, comparable to phenolic plastic. The thermal conductivity of graphite decreases with temperature as shown in Fig.3.10.
What is the SPECIFI C heat of graphene?
Specifi c heat of graphene and graphite. The specific heat, C , of a material represents the change in energy density U when the temperature changes by 1 K, C = d U /d T , where T is the absolute temperature.
How are the vibration waves represented in graphite?
In graphite, it occurs essentially by lattice vibration and is represented by the following relationship: In a polycrystalline materials, the waves are scattered by crystallite boundaries, lattice defects, and other phonons.
How is thermal conductivity related to lattice vibration?
The thermal conductivity (K) is the time rate of transfer of heat by conduction. In graphite, it occurs essentially by lattice vibration and is represented by the following relationship: