Dimensionless capacitance measurement

The dimensionless Lewis number measures the ratio of the heat capacitance term and... 

From the mathematical viewpoint, the diffusion problem (4.3.1)-(4.3.3) is equivalent to the problem on the electric field of a charged conductive body in a homogeneous charge-free dielectric medium. Therefore, the mean Sherwood number in a stagnant fluid coincides with the dimensionless electrostatic capacitance of the body and can be calculated or measured by methods of electrostatics. 

The dielectric constant of plastic materials is measured as specified in ASTM D150. It is a dimensionless factor derived by dividing the parallel capacitance of the system with a plastic material by that of an equivalent system with a vacuum as a dielectric. The lower the number, the better the performance of the material as an insulator. 

The dielectric constant K is the measme of the ability of the material to store the electric charge relative to vacuinn, a dimensionless quantity. The dielectric constant value of ceramics varies at room temperature in the range from 5.5 to well above 10, depending on the type of ceramic (i.e., composition), the temperature and the frequency of operation, the particle size, and the purity of the material. The K values increase upon temperature increase for most ceramics. Often, dielectric constant values are provided with measurements conducted at 1 MHz. Measurements also indicate a strong dependence of the dielectric constant value on the frequency of operation a decline in K is often observed upon a frequency increase. Often, a low dielectric constant is desired to avoid capacitance effect. Typical values of K are 9.7, 6.8, 9.9, and 40, for conventional alumina, beryllia, AIN, and silicon carbide, respectively. 

Relative permittivity (dielectric constant) A measure of the reduction of the potential energy of interaction between the charges on going from vacuum to a medium (such as gas or hquid). The dimensionless relative permittivity of a substance is measured by comparing the capacitance of a capacitor with (C) and without (Cg) the sample present, according to = C/Cg. The name dielectric constant is a misnomer because it is indeed not a constant each solvent has its own value. For example, melting constant or boiling constant are not used. 

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