Electric Flux Density in Electric Field

The electric flux density is an important concept in the study of electric fields. It measures the amount of electric flux passing through a given area per unit area. This flux density is represented by the symbol D and is typically measured in units of coulombs per square meter (C/m²).

Explanation of the Correct Answer: Option B

The correct answer, option B, states that electric flux density is the ratio of flux lines crossing a surface to the surface area. Let's break this down further to understand why this is the correct answer.

- Electric Flux: Electric flux is a measure of the electric field passing through a given area. It is represented by the symbol Φ and is equal to the dot product of the electric field E and the area vector A. Mathematically, it can be expressed as Φ = E · A.

- Flux Lines: Flux lines, also known as electric field lines, are used to visualize the electric field. They represent the direction and magnitude of the electric field at different points in space. The density of these lines represents the strength of the electric field.

- Surface Area: In the context of electric flux density, the surface area refers to the area of an imaginary surface through which the electric flux is passing. This surface can be of any shape or size, and the electric flux passing through it depends on the orientation of the surface with respect to the electric field.

- Ratio of Flux Lines Crossing a Surface and the Surface Area: The electric flux density, D, is defined as the electric flux passing through a given surface divided by the surface area. Mathematically, it can be expressed as D = Φ / A.

By dividing the electric flux by the surface area, we get the electric flux density, which represents the concentration of electric flux passing through a unit area. This ratio gives us a measure of how strong the electric field is in a particular region.

Therefore, option B is the correct answer because it accurately describes the relationship between electric flux lines, surface area, and the calculation of electric flux density.