Question

Dielectric constant of a material measures

• A. \( \text{Electrical conductivity} \)
• B. \( \text{Polarizability in electric field} \)
• C. \( \text{Magnetic susceptibility} \)
• D. \( \text{Optical absorption} \)

Hint:

Dielectrics do not conduct electricity; they polarize! High dielectric constant always indicates high polarizability under an electric field.

Answer 1

The Correct Option is B

Concept: The dielectric constant (\( \varepsilon_r \)), or relative permittivity, of a material quantifies its capacity to store electrical energy under the influence of an external electric field. This storage occurs via the displacement of electrical charges within the atoms or molecules, a phenomenon termed electrical polarization.

Step 1: Defining Dielectric Response
When an insulating (dielectric) material is subjected to an external electric field, the positive charges shift slightly along the direction of the field, and negative charges shift in the opposite direction. This produces electric dipoles throughout the volume of the material. The extent of this dipole formation per unit volume defines the polarizability.

Step 2: Differentiating Material Properties
- Electrical conductivity measures a material's capability to allow a continuous flow of free electric charges, which is characteristic of conductors rather than dielectrics. - Magnetic susceptibility measures the degree of magnetization of a material in response to an applied magnetic field. - Optical absorption evaluates how much light energy a material attenuates or retains per unit path length. - Polarizability directly relates to how easily the charge distribution in a material can be distorted by an electric field, which is exactly what the dielectric constant characterizes.