What is electric polarisation class 12?
2 Answers
Electric polarization is a concept in physics, especially relevant in the context of electrostatics and dielectrics, typically covered in Class 12 Physics. It describes how materials respond to electric fields, leading to the development of dipole moments within the material. Here's a detailed breakdown:
### What is Electric Polarisation?
**Electric Polarisation** refers to the process by which the positive and negative charges within a dielectric material (an insulator) are displaced when subjected to an external electric field. This displacement creates an internal electric field within the material, which affects its overall behavior in the field.
### How It Works
1. **Application of Electric Field**: When an external electric field is applied to a dielectric material, it exerts forces on the bound charges within the material. For instance, in a neutral atom, the positive nucleus and negative electrons are displaced in opposite directions.
2. **Charge Separation**: This displacement causes a separation of charge within the atoms or molecules of the material. This separation results in the formation of electric dipoles.
3. **Formation of Dipole Moments**: Each dipole moment is a vector quantity pointing from the negative charge to the positive charge. The net effect of all these dipole moments within the material leads to what is termed as electric polarization.
4. **Polarization Vector**: The average dipole moment per unit volume of the material is called the polarization vector **P**. It is mathematically expressed as:
\[
\mathbf{P} = \frac{\mathbf{p}}{V}
\]
where **p** is the dipole moment and **V** is the volume of the material.
### Effects of Electric Polarisation
1. **Electric Field Inside a Dielectric**: The polarization of the material affects the internal electric field. The field within the dielectric is less than the applied external field due to the opposing electric field generated by the polarization.
2. **Dielectric Constant**: Polarization is related to the dielectric constant (or relative permittivity) of the material. The dielectric constant is a measure of how easily a material can be polarized. It influences how much the material reduces the effective electric field within it compared to a vacuum.
3. **Bound Charges**: Polarization results in bound surface and volume charges within the dielectric material. These are not free charges like those in conductors but are related to the displacement of bound charges within atoms or molecules.
### Mathematical Representation
The relationship between the electric displacement field **D**, the electric field **E**, and the polarization **P** in a dielectric material is given by:
\[
\mathbf{D} = \epsilon_0 \mathbf{E} + \mathbf{P}
\]
where **ε₀** is the permittivity of free space. This equation shows how the total electric displacement field **D** is influenced by both the applied electric field and the material's polarization.
### Key Points to Remember
- **Polarization** is a response of dielectric materials to an external electric field.
- It results in the formation of electric dipoles within the material.
- **Polarization Vector (P)** quantifies the degree of polarization in a material.
- **Dielectric Constant** is a measure of a material's ability to be polarized.
- The polarization affects the internal electric field and influences the material’s behavior in electric fields.
Understanding electric polarization is crucial for comprehending how insulators work in various applications, from capacitors to insulating materials in electronic devices.
### What is Electric Polarisation?
**Electric Polarisation** refers to the process by which the positive and negative charges within a dielectric material (an insulator) are displaced when subjected to an external electric field. This displacement creates an internal electric field within the material, which affects its overall behavior in the field.
### How It Works
1. **Application of Electric Field**: When an external electric field is applied to a dielectric material, it exerts forces on the bound charges within the material. For instance, in a neutral atom, the positive nucleus and negative electrons are displaced in opposite directions.
2. **Charge Separation**: This displacement causes a separation of charge within the atoms or molecules of the material. This separation results in the formation of electric dipoles.
3. **Formation of Dipole Moments**: Each dipole moment is a vector quantity pointing from the negative charge to the positive charge. The net effect of all these dipole moments within the material leads to what is termed as electric polarization.
4. **Polarization Vector**: The average dipole moment per unit volume of the material is called the polarization vector **P**. It is mathematically expressed as:
\[
\mathbf{P} = \frac{\mathbf{p}}{V}
\]
where **p** is the dipole moment and **V** is the volume of the material.
### Effects of Electric Polarisation
1. **Electric Field Inside a Dielectric**: The polarization of the material affects the internal electric field. The field within the dielectric is less than the applied external field due to the opposing electric field generated by the polarization.
2. **Dielectric Constant**: Polarization is related to the dielectric constant (or relative permittivity) of the material. The dielectric constant is a measure of how easily a material can be polarized. It influences how much the material reduces the effective electric field within it compared to a vacuum.
3. **Bound Charges**: Polarization results in bound surface and volume charges within the dielectric material. These are not free charges like those in conductors but are related to the displacement of bound charges within atoms or molecules.
### Mathematical Representation
The relationship between the electric displacement field **D**, the electric field **E**, and the polarization **P** in a dielectric material is given by:
\[
\mathbf{D} = \epsilon_0 \mathbf{E} + \mathbf{P}
\]
where **ε₀** is the permittivity of free space. This equation shows how the total electric displacement field **D** is influenced by both the applied electric field and the material's polarization.
### Key Points to Remember
- **Polarization** is a response of dielectric materials to an external electric field.
- It results in the formation of electric dipoles within the material.
- **Polarization Vector (P)** quantifies the degree of polarization in a material.
- **Dielectric Constant** is a measure of a material's ability to be polarized.
- The polarization affects the internal electric field and influences the material’s behavior in electric fields.
Understanding electric polarization is crucial for comprehending how insulators work in various applications, from capacitors to insulating materials in electronic devices.