Permittivity concepts — assertion–reason Assertion (A): Relative permittivity εr of a material is determined by its atomic and molecular structure. Reason (R): Absolute permittivity ε0 is determined by the atomic structure of the material.
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ABoth A and R are true and R is correct explanation of A
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BBoth A and R are true but R is not correct explanation of A
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CA is true but R is false
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DA is false but R is true
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ENeither A nor R is true
Answer
Correct Answer: A is true but R is false
Explanation
Introduction / Context:This question distinguishes the material-dependent relative permittivity εr from the universal constant ε0 (vacuum permittivity). It tests whether learners can identify which parameter reflects microstructure.
Given Data / Assumptions:
- Electrostatics in linear, homogeneous media.
- Relation ε = ε0 * εr.
- Atomic/molecular polarization mechanisms contribute to εr.
Concept / Approach:ε0 is a physical constant of vacuum and does not depend on any material. By contrast, εr depends on how bound charges in matter polarize under an applied field; it is set by electronic, ionic, and orientational polarizabilities governed by atomic and molecular structure. Therefore, A is true and R is false.
Step-by-Step Solution:Write ε = ε0 εr.Recognize ε0 as constant (property of free space).Connect εr to polarization P via P = ε0(εr − 1)E → material microstructure determines εr.
Verification / Alternative check:Clausius–Mossotti and Debye relations explicitly tie εr to number density and polarizability, confirming the material dependence of εr.
Why Other Options Are Wrong:(a) and (b) incorrectly attribute material dependence to ε0. (d) flips truth values. (e) denies the well-established facts.
Common Pitfalls:
- Confusing absolute and relative permittivity in formulas.
- Assuming ε0 can vary between media; it does not.
Final Answer:A is true but R is false