What Do You Mean By Dielectric Constant?
Non-conducting substances, which can hold an electrostatic charge while dissipating minimal heat energy, refer to dielectric materials. There are several examples of dielectric materials, including air, plastics, glass, more. Different types of dielectrics possess different values for dielectric constant, dipole moment, and polarisation. Look at the concepts of polarization, what is dielectric constant is, applications, and more.
What is Dielectric Material?
A dielectric material or medium is an insulator kind that becomes polarised when it comes in contact with an electric field. Though a dielectric material is a poor conductor of electricity, it can support an electric field. Such kinds of materials are widely used in components like radios and capacitors. Some types of dielectric materials are solid, some are fluids, and some are gases in nature. Some of the examples of dielectric materials include:
Solid dielectric materials- Plastic, Ceramic, Mica, and Glass
Dielectric Liquid- Water
Dielectric Gas- Dry air
Applications of Dielectric Medium
The dielectric material contains a high number of dipoles. Thus, when subjected to an external electric field, the positive end of one dipole gets induced towards the negative of another dipole. It forms a chain of alternate charge polarities throughout the dielectric material. Such kind of alignment leads to the formation of an electric field. Hence, among the different uses of dielectric materials, its main use is in the manufacturing of capacitors.
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The above diagram shows the dielectric material. It shows when an external electrostatic field is applied, the dielectric medium gets polarised — additionally, dielectric stores electric charge when an electric field is introduced.
Moreover, by introducing a dielectric medium between the capacitor plates, the capacity of the capacitor can be improved. Another best application of dielectric material is its use to store energy.
What is the Concept of Polarization in Polar and Nonpolar Molecules?
Insulators are bad conductors of electricity and heat due to the absence of free moving charges. Unlike metals, there is no flow of current in insulators when placed in an external electrostatic field. Instead of current flow, polarisation occurs in insulators on the application of the electric field.
The extent of polarisation generally depends on the types of dielectric material. The charges in these materials do not move completely, but there is only a slight movement from their rest position. The polarity of molecules is generally decided by the nature of bonds existing in molecules.
Dielectric Polarization in Polar Molecule
Polar molecules have permanent dipoles due to the bonds. Some of the examples of polar molecules are CO2, H2O, and more. However, the dipoles in a polar molecule are randomly oriented due to a thermal effect. That’s why the dipole moment of the polar molecules cancels out and hence, there is a zero-dipole moment.
On the application of the electric field, the individual dipole moments align themselves in the electric field direction. According to the properties of dielectric materials, nature, bonds, and orientation remain constant inside the polar molecule. The extent to which the polar molecule gets polarised is directly related to the thermal energy and strength of the external field.
Dielectric Polarization in Non-polar Molecule
A molecule without a dipole refers to a non-polar molecule. N2, O2, H2 are a few examples of non-polar molecules. The charges are equally distributed in these types of molecules. On applying the electric field, the positive and negative charges having opposite polarities experience a force in the opposite direction. As a result, the electron cloud of a nonpolar molecule gets displaced towards attraction that causes an induced dipole moment. After acknowledging what is dielectric, students can understand why non-polar molecules lose polarity after the removal of the electric field.
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The above diagram shows a nonpolar molecule unpolarised and polarised. The non-polar molecule gets polarised when an external electric field is applied to it. It results in distortion of electrons at the point of attraction.
How To Calculate Dipole Polarization?
The application of the dielectric constant is due to the introduction of the electric field across the material irrespective of whether a dielectric is polar or nonpolar. The polarisation referred to the dipole moment of a material per unit volume and is denoted by:
P = XₑE
Where Xₑ denotes the dielectric material property, also known as electric susceptibility of the dielectric medium.
E represents the applied electric field.
P represents the polarisation.
Apart from the dielectric medium, another crucial parameter in calculating polarisation is the dielectric constant.The dielectric constant of dielectric material is the ratio of the permittivity of the medium to the permittivity of the free space.
Conclusion
This is all about dielectric polarization and, dielectric constant and their related concepts. Understand the basic concept of this topic and find out how to calculate it in polar and non-polar molecules.
FAQs on Dielectric Polarization in Polar and Non-polar Material and Dielectric Constant
1. What is a dielectric material, and why is it different from a standard conductor?
A dielectric material is an electrical insulator that can be polarised by an applied electric field. Unlike a conductor, which has abundant free electrons to conduct electricity, a dielectric's electrons are tightly bound to their atoms. When placed in an external electric field, these materials don't conduct a current, but instead, their charges shift slightly, creating a dipole moment. This ability to support an electrostatic field with minimal energy loss makes them essential in components like capacitors.
2. What are the key differences between polar and non-polar dielectrics?
The primary differences between polar and non-polar dielectrics lie in their molecular structure and behaviour in an electric field:
Molecular Structure: Polar dielectrics (e.g., H₂O, HCl) have an asymmetric shape, and the centres of positive and negative charges do not coincide, resulting in a permanent dipole moment for each molecule.
Non-polar dielectrics (e.g., H₂, O₂, CO₂) have a symmetric shape, and the centres of positive and negative charges coincide, resulting in a zero net dipole moment in the absence of an electric field.
Behaviour in an Electric Field: In polar dielectrics, the external field aligns the already existing, randomly oriented dipoles. In non-polar dielectrics, the external field induces a dipole moment by stretching the molecule and separating the charge centres.
3. What are some common examples of polar and non-polar dielectric materials?
Examples help distinguish between the two types based on their molecular structure:
Polar Dielectric Examples: These materials have molecules with a built-in dipole moment. Common examples include water (H₂O), ammonia (NH₃), hydrogen chloride (HCl), and alcohol.
Non-polar Dielectric Examples: These materials have symmetric molecules with no initial dipole moment. Common examples include hydrogen (H₂), oxygen (O₂), nitrogen (N₂), carbon dioxide (CO₂), mica, glass, and plastics like Teflon.
4. How does dielectric polarization occur in a non-polar dielectric material?
In a non-polar dielectric, each molecule initially has a zero dipole moment because its positive and negative charge centres coincide. When an external electric field (E₀) is applied, it exerts a force on the charges. The positive nucleus is pushed in the direction of the field, while the electron cloud is pulled in the opposite direction. This separation of charges creates or 'induces' a small dipole moment in each molecule. This phenomenon is called dielectric polarization, and the induced dipoles align with the external field.
5. How does dielectric polarization occur in a polar dielectric material?
In a polar dielectric, molecules possess a permanent dipole moment but are randomly oriented due to thermal agitation, so the net dipole moment of the material is zero. When an external electric field is applied, it exerts a torque on each molecular dipole. This torque tries to align the dipoles with the direction of the field. While thermal energy resists perfect alignment, a net alignment occurs, resulting in a non-zero dipole moment for the material as a whole. This alignment process is known as dielectric polarization.
6. What does the dielectric constant (K) of a material signify?
The dielectric constant (K), also known as relative permittivity (εr), is a dimensionless factor that indicates how effectively a dielectric material can reduce the external electric field strength within it. It is defined as the ratio of the strength of the applied external electric field (E₀) to the strength of the net electric field (E) inside the dielectric. A higher value of K means the material is more effective at storing energy by polarising and reducing the internal electric field.
7. Why does the net electric field inside a dielectric decrease when it is placed in an external field?
When a dielectric is placed in an external electric field (E₀), it undergoes polarization. This means the molecular dipoles (whether permanent or induced) align to create an internal electric field (Ep) within the dielectric that opposes the external field. The net electric field (E) inside the material is the vector sum of the external field and the opposing internal field: E = E₀ - Ep. Because the internal field counteracts the external one, the overall electric field strength inside the dielectric is reduced.
