Permittivity
Permittivity - Related Videos
01:26
Susceptibility, Permittivity and Dielectric Constant
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2025
When placed in an external electric field, a dielectric material gets polarized. The charge density in the dielectric material is given by the sum of the bound and free charge densities, while the total charge density can also be written in terms of the total electric field. The bound charge density can be measured in terms of polarization, leading to the relationship between electric displacement and polarization. The polarization is proportional to the electric field for the linear...
08:56
Capacitance
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2023
Source: Yong P. Chen, PhD, Department of Physics & Astronomy, College of Science, Purdue University, West Lafayette, IN This experiment will use commercial capacitors and a parallel plate capacitor to demonstrate the concept of capacitance. A capacitor stores opposite charges on two conductors, for example two opposite metal plates, leading to a potential difference (voltage drop) between the two conductors. The amount of charge on each conductor is proportional to this voltage drop, with...
05:28
Clinical Imaging of Microwave Mammography
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2025
This protocol describes the imaging procedure of a microwave imaging device for breast imaging.
09:39
Optical Biosensing
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2023
Optical biosensors utilize light to detect the binding of a target molecule. These sensors can utilize a label molecule, which produces a measurable signal such as fluorescence, or these sensors can be label-free and use the changes in optical properties, such as refractive index, to sense for the binding of the target molecule. This video introduces both label and label-free optical biosensors, demonstrates their use in the laboratory, and shows some applications of the technology.
13:44
Simulation, Fabrication and Characterization of THz Metamaterial Absorbers
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Cited by 6 •
2012
This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.
FAQs
The key microscopic effect is polarization: an applied field causes bound charges within a material to shift slightly or rotate. These changes modify the material’s internal electric field and contribute to electric displacement. The resulting response explains why different materials alter an applied field in different ways.
The relation D = εE connects electric displacement with the applied electric field through permittivity. For a specified field, the value of ε indicates how strongly the material supports displacement. This relationship provides a quantitative basis for comparing material responses and incorporating them into electric-field calculations.
Permittivity can vary with frequency because the material’s polarization response depends on how rapidly the electric field changes. Microscopic charge shifts or rotations may respond differently at different frequencies, changing the resulting internal field and electric displacement. This dependence matters when materials are used in systems operating across different frequency ranges.
Temperature and material structure are important variables because they can alter how a material responds to an electric field. Changes in either factor may modify polarization and therefore the value of permittivity. Accounting for these dependencies helps explain why the same material may not exhibit identical electrical behavior under every physical condition.
Relative permittivity compares a material’s permittivity with the permittivity of vacuum, so it expresses the response as a ratio rather than as the material’s direct permittivity value. It is also commonly called the dielectric constant. This comparison provides a convenient way to describe how strongly a material differs from vacuum.
Permittivity helps guide material selection and design decisions for capacitors and insulators because it characterizes the material’s response to an electric field. Designers can consider how polarization and electric displacement will behave in the selected material. Its dependence on frequency, temperature, and structure is relevant when operating conditions vary.
Permittivity influences how electric fields and electromagnetic waves behave in engineered systems. In transmission lines and sensors, its value helps characterize material-dependent electrical behavior, while in electromagnetic devices it supports control of wave propagation. These applications extend beyond isolated material study to practical systems that shape, transmit, or detect electromagnetic effects.