MCQ
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 :
  • A
    (A) is correct but $(\mathbf{R})$ is not correct
  • B
    Both (A) and (R) are correct but (R) is not the correct explanation of (A)
  • C
    Both (A) and (R) are correct and (R) is the correct explanation of (A)
  • D
    (A) is not correct but ( $\mathbf{R}$ ) is correct

Answer

D. (A) is not correct but ( $\mathbf{R}$ ) is correct
A : Since polar dielectrics are randomly oriental $\overrightarrow{\mathrm{P}}_{\mathrm{net}}=\overrightarrow{0}$.
$R$ : If $\vec{E}$ is absent, polar dielectric remain polar & are randomly oriented.

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