1 Answer
The **electric field** and **electric flux density** are closely related concepts in electromagnetism, but they are not the same. Let me break it down for you in simple terms:
1. **Electric Field (E):**
- This is a vector field that describes the force per unit charge exerted on a test charge placed in space. It tells us how strong the electric force is and in what direction it would act on a positive test charge.
- Its units are **volts per meter (V/m)**.
2. **Electric Flux Density (D):**
- This is also known as the **electric displacement field**. It tells us how much electric flux (i.e., the number of electric field lines) is passing through a given area.
- The electric flux density accounts for both the free charges (charged particles like electrons or protons) and the bound charges (charges bound within materials like dielectric substances).
- Its units are **coulombs per square meter (C/m²)**.
### Relationship between E and D:
The relationship between the electric field **E** and the electric flux density **D** is given by the equation:
\[
\mathbf{D} = \epsilon \mathbf{E}
\]
Where:
- **D** is the electric flux density (C/m²),
- **E** is the electric field (V/m),
- **ε** (epsilon) is the **permittivity** of the material through which the field is present. It’s a constant that describes how easily the material allows electric field lines to pass through it.
- In **vacuum**, the permittivity is denoted as **ε₀** (the permittivity of free space), which is approximately **8.854 × 10⁻¹² C²/N·m²**.
- In a **material** (like air or a dielectric), permittivity becomes **ε = ε₀ * εr**, where **εr** is the relative permittivity (dielectric constant) of the material.
### In Summary:
- The electric field **E** describes how the field influences charges.
- The electric flux density **D** describes the flow of the electric field through a medium, and it takes into account the material's response to the electric field (how easily the material can "conduct" the field).
Essentially, the electric flux density **D** is a way to describe the electric field in terms of both the material’s properties and the field itself.
1. **Electric Field (E):**
- This is a vector field that describes the force per unit charge exerted on a test charge placed in space. It tells us how strong the electric force is and in what direction it would act on a positive test charge.
- Its units are **volts per meter (V/m)**.
2. **Electric Flux Density (D):**
- This is also known as the **electric displacement field**. It tells us how much electric flux (i.e., the number of electric field lines) is passing through a given area.
- The electric flux density accounts for both the free charges (charged particles like electrons or protons) and the bound charges (charges bound within materials like dielectric substances).
- Its units are **coulombs per square meter (C/m²)**.
### Relationship between E and D:
The relationship between the electric field **E** and the electric flux density **D** is given by the equation:
\[
\mathbf{D} = \epsilon \mathbf{E}
\]
Where:
- **D** is the electric flux density (C/m²),
- **E** is the electric field (V/m),
- **ε** (epsilon) is the **permittivity** of the material through which the field is present. It’s a constant that describes how easily the material allows electric field lines to pass through it.
- In **vacuum**, the permittivity is denoted as **ε₀** (the permittivity of free space), which is approximately **8.854 × 10⁻¹² C²/N·m²**.
- In a **material** (like air or a dielectric), permittivity becomes **ε = ε₀ * εr**, where **εr** is the relative permittivity (dielectric constant) of the material.
### In Summary:
- The electric field **E** describes how the field influences charges.
- The electric flux density **D** describes the flow of the electric field through a medium, and it takes into account the material's response to the electric field (how easily the material can "conduct" the field).
Essentially, the electric flux density **D** is a way to describe the electric field in terms of both the material’s properties and the field itself.