JEE Main 2025 — Electrostatics Question with Solution
From: JEE Main 2025 (Online) 2nd April Evening Shift
Question
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Net dipole moment of a polar linear isotropic dielectric substance is not zero even in the absence of an external electric field.
Reason (R) : In absence of an external electric field, the different permanent dipoles of a polar dielectric substance are oriented in random directions.
In the light of the above statements, choose the most appropriate answer from the options given below :
Choose an option
Show full solutionCorrect option: C
Step-by-step explanation
Assertion (A): The net dipole moment of a polar linear isotropic dielectric substance is not zero, even when there is no external electric field.
Reason (R): In the absence of an external electric field, the different permanent dipoles in a polar dielectric substance are oriented in random directions.
Explanation:
Assertion (A): The statement is incorrect. In a polar linear isotropic dielectric substance, the net dipole moment is zero when an external electric field is absent. This is because the dipoles within the material are randomly oriented and cancel each other out.
Reason (R): The statement is correct. In the absence of an external electric field, the dipoles in a polar dielectric substance remain inherently polarized but are oriented randomly. This randomness in orientation leads to a cancellation of the net dipole moment.
Therefore, while the reason is correct, it does not support the validity of the assertion as stated.
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This is a previous-year question from JEE Main 2025, covering the Electrostatics chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.