Education Journalist | Study Abroad Lead
Dielectric material or a medium is typically an electrical insulator that can be polarized by applying an electric field. When positioned in an electric field, no electric charge streams via dialectic material as they don’t contain loosely bound or free electrons which may float through the material, rather, they slightly deviate from their intermediate equilibrium position which in return induces dielectric polarization.
| Table of Content |
Key Takeaways: Dielectric Material, Conductor, Insulator, Electric Field, Electric Charges, Dielectric Polarization, Electron, Electric insulator, Voltage
What is Dielectric Material?
[Click Here for Sample Questions]
Dielectric material is a poor conductor of electricity which can also be considered as an insulator. This signifies that on applying a particular quantity of voltage, no current can pass via the material. However, there may occur a specific amount of adjustments on the atomic scale.
Dielectric Material
It is referred to as a non-metallic material that has a specific high resistance, negative temperature coefficient of resistance, and large insulation resistance. The dielectric materials are mostly solids. In such cases where the dielectric materials are composed of weakly bonded molecules, it can be observed that the molecules reorient themselves to align their symmetry axes with the field.
Also Read:
| Related Articles | ||
|---|---|---|
| Electrical conductor | Potential difference | Ohm’s law |
| Electric charges and field | Gauss Law | Electric Flux |
Dielectric Properties
[Click Here for Sample Questions]
Dielectric Properties of a material are defined as the elemental molecular property in the materials capable of impending electron movement inducing polarization within the material on exposure to an external electric field. The main properties of dielectric materials comprise electric susceptibility, dielectric polarization, dielectric dispersion, dielectric relaxation, tenability, etc.
The properties of dielectric materials have been mentioned below:
Electric Susceptibility
This property of dielectric measures how efficiently the material will be polarized when subjected to an electric field. Electric susceptibility also measures the material’s electric permeability.
Dielectric Polarization
The electric dipole moment measures the negative and positive charge separation within the system. The rise in dielectric properties is governed by the relationship between the moment of dipole (M) and the electric field (E). The atom returns to its original state when the applied electric field is removed.
Dielectric Polarization
Dielectric Breakdown
Upon the application of higher electrical fields, the insulator begins to conduct and act as a conductor. The dielectric materials lose their dielectric properties under such conditions. This phenomenon is described as the dielectric breakdown. This process is irreversible which leads to the failure of dielectric material.
Dielectric Breakdown
Dielectric Dispersion
This property of dielectric can be understood by the expressions below:
P(t) = maximum polarization attained by the dielectric.
P(t) = P [1 – exp ( – t/tr) ]
Where,
tr = Relaxation time for a particular polarization process.
The period of relaxation varied with various mechanisms of polarization. The process of Electric polarization followed by ionic polarization is very rapid whereas the orientation polarization is quite slower than the ionic polarization.
Apart from the above-mentioned properties, there are a few other properties of dielectric material which is as follows:
- The energy gap between the electric materials is huge.
- The dielectric material consists of high resistivity with a negative temperature coefficient of resistance and high insulation resistance.
- There exists a strong attraction between the electrons and the parent nucleus.
- The dielectric materials have very low electrical conductivity because they don’t contain free electrons to carry current.
Also Read:
| Related Articles | ||
|---|---|---|
| Electrical Cable | Potential Due to Point Charge | Potential Due to Electric Dipole |
| Equipotential Surface | Combination of Capacitors | conducting plates |
Types of Dielectric Materials
[Click Here for Sample Questions]
Depending upon the type of molecules present in the material, a dielectric material can be categorized into two types. The various two types of dielectrics are as follows:
Polar Dielectric
In polar dielectrics, the centre of mass of positive particles doesn't overlap with that of the negative particles. At this instant, there exists a dipole moment. The molecules display an asymmetrical shape and align with the electric field when an electric field is applied. Upon the removal of the electric field, the random dipole moment is observed and the net dipole moment in the molecules turns out to be zero.
For example, H2O, CO2.
Types of Dielectric Materials
Non-polar Dielectric
Inside the non-polar dielectrics, the centre of mass of the positive particles and the negative particles coincides. These molecules don’t have any dipole moment and the molecules are in the form of symmetry.
Example: H2, O2, N2.
Application of Dielectric Material
[Click Here for Sample Questions]
The list of applications of the dielectric material has been mentioned in the list below:
- They are used in the form of capacitors for storing energy.
- In a transformer, the dielectric material can be used as an insulator as well as a cooling agent.
- Dielectric material with high permittivity can be used to enhance the performance of semiconductors.
- A specially processed dielectric material named electret acts as an electrostatic which is equivalent to magnets.
- Ceramic dielectrics are used in the oscillator dielectric resonator.
- Liquid dielectrics are also considered useful in various ways such as an insulating & cooling medium for transformers, earth reactors, and shunt reactors, etc.
Dielectric Capacitor
Things to Remember
- Dielectric materials are considered to be poor conductor of electricity.
- It indicates the ability of a material to store energy.
- There are two types of dielectric i.e. polar, and non-polar.
- A vacuum is considered to be a perfect dielectric medium.
- The dielectric term is typically used to refer to the material having superior polarization.
- They can be used in liquid crystal displays.
- These types of materials also act as an insulator as well as cooling agents for the transformers.
- Various types of dielectric material used in capacitors include ceramic dielectric, glass, paper, & mica dielectric.
- Insulators and dielectric materials are not similar to each other.
Read More:
Sample Questions
Ques: State the differences between an insulator and a dielectric material. (3 marks)
Ans: The differences between the insulator and the dielectric material have been mentioned in the table below:
| Dielectrics | Insulators |
|---|---|
| The material which can develop an electric field with a minimal loss of energy is defined as a dielectric. | A substance that poses low conductivity and which hinders the flow of current is defined as an insulator. |
| These are weakly bonded as compared to the insulators | They are covalently bonded |
| They store charges | They obstruct charges |
| They have application in power cables, capacitors and more | They are used in the high voltage system and conducting wires, etc. |
Ques: Are all insulators dielectric? If yes, explain. (2 marks)
Ans: All the dielectrics can be considered as insulators but the reverse does not hold true. The insulators cannot conduct electricity in an electric field due to the absence of free electrons whereas the dielectrics are the insulators which can be polarized.
Ques: What happens when the voltage source is removed from the dielectric material? (2 marks)
Ans: Upon the removal of the voltage source from the dielectric material, the material either returns to its original non-polarized state or remains in its polarized state if the molecular bonds in the dielectric materials are weak.
Ques: What is dielectric polarization? (2 marks)
Ans: Dielectric polarization is the phenomenon that causes the positive charges to stream in the direction of the electric field and the negative charges to shift in the opposite direction of the electric field.
This phenomenon of dielectric polarization yields an internal electric field which in turn reduces the overall electric field within the dielectric material. Ques: Give some examples of dielectric material.
Ques: What are dielectric materials? (2 marks)
Ans: The dielectric materials are used to store energy. They exist in the forms of solid, liquid, and gases. The examples of the dielectric materials are listed below:
- Solid dielectrics: ceramic, mica, glass, and plastic
- Dielectric liquid: distilled water
- Dielectric gas: dry air, vacuum, helium, and nitrogen
Ques: What is the relaxation time? (2 marks)
Ans: The Relaxation time can be generally described as the time taken by the atom to reach its original state.
Ques: Define the term dielectric constant. (2 marks)
Ans: The dielectric constant is expressed as the ability of an object to preserve as much energy in the form of an electrical field as up to the extent where a substance concentrates an electrical flux. It can also be considered as the ratio of the permittivity of an object to the permittivity of free space.
Ques: What are the dielectric properties of food? (2 marks)
Ans: There exist few dielectric properties which influences the food which are as follows:
- Frequency of the microwave.
- The temperature.
- Density of the material.
- Structure & composition of the material being used.
- Quantity of water/ liquid present in the food.
Ques. Define the dielectric constant of a medium. What is its unit? [CBSE 2011] (3 marks)
Ans. Dielectric When a dielectric slab is introduced between the plates of a charged capacitor or in the region of the electric field, an electric field EP induces inside the dielectric due to induced charge on dielectric in a direction opposite to the direction of the applied external electric field. Hence, the net electric field inside the dielectric gets reduced to E0 – EP, where E0 is the external electric field. The ratio of applied external electric field and a reduced electric field is known as dielectric constant K of the dielectric medium, i.e.
Ques. What are Free Charges and Bound Charges inside a Conductor? (5 marks)
Ans.
- In a metal, the outer (valence) electrons are free to move. These electrons are free for moving within the metal but not free to leave the metal. These free electrons are free charges inside a conductor and are a cause for the conduct of electricity by conductors.
- The bound charges are those positive ions that are made up of the nuclei and the bound electrons remain in their fixed positions.
Some important results regarding electrostatics of conductors are given as below:
- Inside a conductor, the electric field is zero.
- The interior of a conductor can have no excess charge in a static situation.
- Electric field just outside a charged conductor is perpendicular to the surface of the conductor at every point.
For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates
Check-Out:
Comments