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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. (1) Both (A) and (R) are correct but (R) is not the correct explanation of (A) (2) (A) is correct but (R) is not correct (3) (A) is not correct but (R) is correct (4) Both (A) and (R) are correct and (R) is the correct explanation of (A)

1. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
2. (A) is correct but (R) is not correct
3. (A) is not correct but (R) is correct
4. Both (A) and (R) are correct and (R) is the correct explanation of (A)

Correct answer: (A) is not correct but (R) is correct

Solution

The assertion is incorrect because the net dipole moment of a polar linear isotropic dielectric is zero in the absence of an external electric field, as the permanent dipoles average out due to their random orientation. The reason is correct, as it accurately describes the random orientation of dipoles when no external field is present.

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