Why electric field inside a dielectric decreases due to polarization?
2 Answers
To understand why the electric field inside a dielectric material decreases due to polarization, it's important to break down the concepts of electric field, dielectric, and polarization. Let's dive into the details.
### 1. **Electric Field and Dielectrics**
- **Electric Field (E):** The electric field (\( \mathbf{E} \)) is a vector field that represents the force per unit charge exerted on a charged particle placed in the field. It influences how charges move within a material.
- **Dielectric Material:** A dielectric is an insulating material that does not conduct electricity but can be polarized by an electric field. When a dielectric material is placed in an electric field, it becomes polarized.
### 2. **Polarization of Dielectrics**
- **Polarization (\( \mathbf{P} \)):** Polarization refers to the alignment of electric dipoles within a material under the influence of an external electric field. Each dipole consists of positive and negative charges separated by a small distance. In a dielectric, these dipoles can either be intrinsic (inherent to the material) or induced by an external electric field.
- **Induced Dipoles:** When an external electric field is applied to a dielectric material, it induces dipole moments in the material. These dipoles tend to align themselves with the external field, creating a polarization effect.
### 3. **Mechanism of Decrease in Electric Field**
The key to understanding why the electric field inside a dielectric decreases due to polarization lies in how the polarization affects the internal electric field.
- **Bound Charges:** Polarization results in the creation of bound charges on the surfaces of the dielectric material. These bound charges are of two types: bound positive charges (associated with the negative end of dipoles) and bound negative charges (associated with the positive end of dipoles).
- **Electric Field Due to Bound Charges:** The bound charges on the surfaces of the dielectric material produce their own electric field, which is superimposed on the original external electric field. This electric field due to the bound charges opposes the external electric field.
### 4. **Superposition of Fields**
- **Total Electric Field:** The total electric field (\( \mathbf{E}_{\text{total}} \)) inside the dielectric is the vector sum of the applied electric field (\( \mathbf{E}_{\text{applied}} \)) and the electric field produced by the bound charges (\( \mathbf{E}_{\text{bound}} \)):
\[
\mathbf{E}_{\text{total}} = \mathbf{E}_{\text{applied}} + \mathbf{E}_{\text{bound}}
\]
- **Opposing Electric Field:** Since the electric field produced by the bound charges (\( \mathbf{E}_{\text{bound}} \)) is in the direction opposite to the applied electric field (\( \mathbf{E}_{\text{applied}} \)), the total electric field inside the dielectric is less than the applied electric field.
### 5. **Mathematical Representation**
The reduction of the electric field inside a dielectric can be quantified by the dielectric constant (\( \kappa \)) or relative permittivity:
- **Relation:** The relationship between the applied electric field (\( E_0 \)) and the electric field inside the dielectric (\( E \)) is given by:
\[
E = \frac{E_0}{\kappa}
\]
where \( \kappa \) (or \( \epsilon_r \)) is the dielectric constant of the material.
### 6. **Physical Interpretation**
The physical interpretation of this phenomenon is that the polarization of the dielectric material creates an internal field that reduces the net electric field within the material. This internal field is effectively shielding the interior from the full force of the applied external electric field.
In summary, the electric field inside a dielectric decreases due to polarization because the polarization creates an opposing field (due to bound charges) that counteracts the applied electric field. This results in a reduced net electric field within the dielectric material.
### 1. **Electric Field and Dielectrics**
- **Electric Field (E):** The electric field (\( \mathbf{E} \)) is a vector field that represents the force per unit charge exerted on a charged particle placed in the field. It influences how charges move within a material.
- **Dielectric Material:** A dielectric is an insulating material that does not conduct electricity but can be polarized by an electric field. When a dielectric material is placed in an electric field, it becomes polarized.
### 2. **Polarization of Dielectrics**
- **Polarization (\( \mathbf{P} \)):** Polarization refers to the alignment of electric dipoles within a material under the influence of an external electric field. Each dipole consists of positive and negative charges separated by a small distance. In a dielectric, these dipoles can either be intrinsic (inherent to the material) or induced by an external electric field.
- **Induced Dipoles:** When an external electric field is applied to a dielectric material, it induces dipole moments in the material. These dipoles tend to align themselves with the external field, creating a polarization effect.
### 3. **Mechanism of Decrease in Electric Field**
The key to understanding why the electric field inside a dielectric decreases due to polarization lies in how the polarization affects the internal electric field.
- **Bound Charges:** Polarization results in the creation of bound charges on the surfaces of the dielectric material. These bound charges are of two types: bound positive charges (associated with the negative end of dipoles) and bound negative charges (associated with the positive end of dipoles).
- **Electric Field Due to Bound Charges:** The bound charges on the surfaces of the dielectric material produce their own electric field, which is superimposed on the original external electric field. This electric field due to the bound charges opposes the external electric field.
### 4. **Superposition of Fields**
- **Total Electric Field:** The total electric field (\( \mathbf{E}_{\text{total}} \)) inside the dielectric is the vector sum of the applied electric field (\( \mathbf{E}_{\text{applied}} \)) and the electric field produced by the bound charges (\( \mathbf{E}_{\text{bound}} \)):
\[
\mathbf{E}_{\text{total}} = \mathbf{E}_{\text{applied}} + \mathbf{E}_{\text{bound}}
\]
- **Opposing Electric Field:** Since the electric field produced by the bound charges (\( \mathbf{E}_{\text{bound}} \)) is in the direction opposite to the applied electric field (\( \mathbf{E}_{\text{applied}} \)), the total electric field inside the dielectric is less than the applied electric field.
### 5. **Mathematical Representation**
The reduction of the electric field inside a dielectric can be quantified by the dielectric constant (\( \kappa \)) or relative permittivity:
- **Relation:** The relationship between the applied electric field (\( E_0 \)) and the electric field inside the dielectric (\( E \)) is given by:
\[
E = \frac{E_0}{\kappa}
\]
where \( \kappa \) (or \( \epsilon_r \)) is the dielectric constant of the material.
### 6. **Physical Interpretation**
The physical interpretation of this phenomenon is that the polarization of the dielectric material creates an internal field that reduces the net electric field within the material. This internal field is effectively shielding the interior from the full force of the applied external electric field.
In summary, the electric field inside a dielectric decreases due to polarization because the polarization creates an opposing field (due to bound charges) that counteracts the applied electric field. This results in a reduced net electric field within the dielectric material.