What happens to electric field due to polarization?
2 Answers
When discussing the electric field in the context of polarization, it's important to understand both the physical concept of polarization and its effect on the electric field. Let's break it down step by step:
### What is Polarization?
**Polarization** refers to the process by which a dielectric material (an insulating material) becomes polarized when exposed to an electric field. In simpler terms, when an external electric field is applied to a dielectric material, the positive and negative charges within the material shift slightly in opposite directions. This separation of charge creates an internal electric field within the material.
### How Does Polarization Affect the Electric Field?
1. **Formation of Electric Dipoles**: When a dielectric material is placed in an electric field, the atoms or molecules within the material become polarized. This means that the positive and negative charges within each atom or molecule are displaced, creating electric dipoles. These dipoles align with the external electric field.
2. **Induced Electric Field**: The dipoles created by polarization generate their own electric field inside the dielectric material. This induced electric field opposes the applied external electric field. In other words, it reduces the overall electric field within the dielectric compared to what it would be if the dielectric were not present.
3. **Electric Field Inside the Dielectric**: The presence of the dielectric material results in a reduction of the electric field inside the material. The electric field inside a dielectric is less than the electric field in a vacuum or air (which is the same as the external field before polarization). The relationship between the electric field inside the dielectric (\(E_{\text{inside}}\)) and the external field (\(E_{\text{external}}\)) is given by:
\[
E_{\text{inside}} = \frac{E_{\text{external}}}{\kappa}
\]
where \(\kappa\) is the dielectric constant of the material. The dielectric constant (\(\kappa\)) is a measure of the material's ability to reduce the electric field.
4. **Reduction of Electric Field**: The electric field inside the dielectric material is reduced due to the polarization effects. The reduction depends on the dielectric constant of the material. A higher dielectric constant means a greater reduction in the electric field.
5. **Electric Displacement Field (\(D\))**: In addition to the electric field (\(E\)), we also consider the electric displacement field (\(D\)). The relationship between \(D\) and \(E\) in a dielectric is given by:
\[
D = \epsilon_0 E + P
\]
where \(\epsilon_0\) is the permittivity of free space and \(P\) is the polarization vector. In terms of the dielectric constant (\(\kappa\)), this can be expressed as:
\[
D = \kappa \epsilon_0 E
\]
### Summary
In summary, polarization affects the electric field in a dielectric material by creating an internal electric field that opposes the external electric field. This opposition reduces the overall electric field within the material. The extent of this reduction is characterized by the dielectric constant of the material. The polarization also affects the electric displacement field, which accounts for both the external electric field and the field due to polarization.
### What is Polarization?
**Polarization** refers to the process by which a dielectric material (an insulating material) becomes polarized when exposed to an electric field. In simpler terms, when an external electric field is applied to a dielectric material, the positive and negative charges within the material shift slightly in opposite directions. This separation of charge creates an internal electric field within the material.
### How Does Polarization Affect the Electric Field?
1. **Formation of Electric Dipoles**: When a dielectric material is placed in an electric field, the atoms or molecules within the material become polarized. This means that the positive and negative charges within each atom or molecule are displaced, creating electric dipoles. These dipoles align with the external electric field.
2. **Induced Electric Field**: The dipoles created by polarization generate their own electric field inside the dielectric material. This induced electric field opposes the applied external electric field. In other words, it reduces the overall electric field within the dielectric compared to what it would be if the dielectric were not present.
3. **Electric Field Inside the Dielectric**: The presence of the dielectric material results in a reduction of the electric field inside the material. The electric field inside a dielectric is less than the electric field in a vacuum or air (which is the same as the external field before polarization). The relationship between the electric field inside the dielectric (\(E_{\text{inside}}\)) and the external field (\(E_{\text{external}}\)) is given by:
\[
E_{\text{inside}} = \frac{E_{\text{external}}}{\kappa}
\]
where \(\kappa\) is the dielectric constant of the material. The dielectric constant (\(\kappa\)) is a measure of the material's ability to reduce the electric field.
4. **Reduction of Electric Field**: The electric field inside the dielectric material is reduced due to the polarization effects. The reduction depends on the dielectric constant of the material. A higher dielectric constant means a greater reduction in the electric field.
5. **Electric Displacement Field (\(D\))**: In addition to the electric field (\(E\)), we also consider the electric displacement field (\(D\)). The relationship between \(D\) and \(E\) in a dielectric is given by:
\[
D = \epsilon_0 E + P
\]
where \(\epsilon_0\) is the permittivity of free space and \(P\) is the polarization vector. In terms of the dielectric constant (\(\kappa\)), this can be expressed as:
\[
D = \kappa \epsilon_0 E
\]
### Summary
In summary, polarization affects the electric field in a dielectric material by creating an internal electric field that opposes the external electric field. This opposition reduces the overall electric field within the material. The extent of this reduction is characterized by the dielectric constant of the material. The polarization also affects the electric displacement field, which accounts for both the external electric field and the field due to polarization.
When a material becomes polarized, the electric field inside and around it is affected by the rearrangement of electric charges within the material. This process of polarization, where the charges shift slightly in response to an external electric field, changes the overall behavior of the electric field in the following ways:
### 1. **Polarization and Bound Charges**
- In a polarized material, the external electric field causes **bound charges** to form, meaning charges that don't leave the material but shift within atoms or molecules. Positive and negative charges move slightly apart within each molecule or atom, creating tiny dipoles.
- The polarization results in **surface bound charges** on the material’s boundary. Positive bound charges accumulate on one surface, while negative bound charges accumulate on the opposite surface.
- These bound charges produce their own internal electric field, which opposes the external applied electric field.
### 2. **Reduction of the Internal Electric Field**
- The internal electric field created by these polarized bound charges works in opposition to the external electric field. As a result, the **net electric field** inside the material is reduced compared to the external electric field.
- The stronger the polarization (i.e., the larger the dipoles inside the material), the more the internal electric field cancels out the external field.
### 3. **Electric Displacement Field (D-field)**
- To describe the combined effect of free charges (from external sources) and bound charges (from polarization), physicists use the **electric displacement field** \( \mathbf{D} \). This is related to the electric field \( \mathbf{E} \) and the polarization \( \mathbf{P} \) by the equation:
\[
\mathbf{D} = \varepsilon_0 \mathbf{E} + \mathbf{P}
\]
where \( \varepsilon_0 \) is the permittivity of free space.
- In materials, \( \mathbf{D} \) accounts for both the external field and the polarization effects, helping to understand the electric field behavior when dielectric (polarizable) materials are involved.
### 4. **Effect on Capacitance (Dielectric Materials)**
- When a dielectric material is placed between the plates of a capacitor, the polarization of the dielectric reduces the effective electric field inside the capacitor. This increases the capacitor’s ability to store charge, thus increasing the **capacitance**.
- The relationship between the permittivity of the dielectric material (a measure of how easily it polarizes) and the electric field is captured by the material's **relative permittivity** \( \varepsilon_r \) or **dielectric constant**. A higher dielectric constant means the material polarizes more, leading to greater reduction in the internal field and higher capacitance.
### 5. **In Homogeneous and Inhomogeneous Materials**
- In **homogeneous materials** (materials with uniform composition), polarization is uniform, and the internal electric field is reduced evenly throughout the material.
- In **inhomogeneous materials** (where the material properties vary), the polarization and internal electric field may vary spatially, leading to more complex electric field distributions.
### 6. **Dielectric Breakdown**
- When the external electric field becomes too strong, the material can no longer sustain the polarization, leading to dielectric breakdown. In this case, the internal electric field can no longer counteract the external field, and the material may become conductive, allowing charges to flow freely.
### Summary of Key Effects:
- **Polarization opposes the external field**, reducing the net electric field inside the material.
- **Surface bound charges** are created, generating their own internal field.
- **Capacitance increases** in dielectric materials due to polarization.
- The **electric displacement field** \( \mathbf{D} \) is used to account for both free and bound charge effects.
Thus, the electric field due to polarization is always influenced by the material's response to an external field, leading to a more complex overall field. Polarization reduces the net electric field inside a dielectric, enhances the material's ability to store charge, and affects the overall electrical properties of devices like capacitors.
### 1. **Polarization and Bound Charges**
- In a polarized material, the external electric field causes **bound charges** to form, meaning charges that don't leave the material but shift within atoms or molecules. Positive and negative charges move slightly apart within each molecule or atom, creating tiny dipoles.
- The polarization results in **surface bound charges** on the material’s boundary. Positive bound charges accumulate on one surface, while negative bound charges accumulate on the opposite surface.
- These bound charges produce their own internal electric field, which opposes the external applied electric field.
### 2. **Reduction of the Internal Electric Field**
- The internal electric field created by these polarized bound charges works in opposition to the external electric field. As a result, the **net electric field** inside the material is reduced compared to the external electric field.
- The stronger the polarization (i.e., the larger the dipoles inside the material), the more the internal electric field cancels out the external field.
### 3. **Electric Displacement Field (D-field)**
- To describe the combined effect of free charges (from external sources) and bound charges (from polarization), physicists use the **electric displacement field** \( \mathbf{D} \). This is related to the electric field \( \mathbf{E} \) and the polarization \( \mathbf{P} \) by the equation:
\[
\mathbf{D} = \varepsilon_0 \mathbf{E} + \mathbf{P}
\]
where \( \varepsilon_0 \) is the permittivity of free space.
- In materials, \( \mathbf{D} \) accounts for both the external field and the polarization effects, helping to understand the electric field behavior when dielectric (polarizable) materials are involved.
### 4. **Effect on Capacitance (Dielectric Materials)**
- When a dielectric material is placed between the plates of a capacitor, the polarization of the dielectric reduces the effective electric field inside the capacitor. This increases the capacitor’s ability to store charge, thus increasing the **capacitance**.
- The relationship between the permittivity of the dielectric material (a measure of how easily it polarizes) and the electric field is captured by the material's **relative permittivity** \( \varepsilon_r \) or **dielectric constant**. A higher dielectric constant means the material polarizes more, leading to greater reduction in the internal field and higher capacitance.
### 5. **In Homogeneous and Inhomogeneous Materials**
- In **homogeneous materials** (materials with uniform composition), polarization is uniform, and the internal electric field is reduced evenly throughout the material.
- In **inhomogeneous materials** (where the material properties vary), the polarization and internal electric field may vary spatially, leading to more complex electric field distributions.
### 6. **Dielectric Breakdown**
- When the external electric field becomes too strong, the material can no longer sustain the polarization, leading to dielectric breakdown. In this case, the internal electric field can no longer counteract the external field, and the material may become conductive, allowing charges to flow freely.
### Summary of Key Effects:
- **Polarization opposes the external field**, reducing the net electric field inside the material.
- **Surface bound charges** are created, generating their own internal field.
- **Capacitance increases** in dielectric materials due to polarization.
- The **electric displacement field** \( \mathbf{D} \) is used to account for both free and bound charge effects.
Thus, the electric field due to polarization is always influenced by the material's response to an external field, leading to a more complex overall field. Polarization reduces the net electric field inside a dielectric, enhances the material's ability to store charge, and affects the overall electrical properties of devices like capacitors.