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Electric Charges and Fields — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsElectric Charges and Fields1 Mark
Question
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): If a conducting medium is placed between two charges, then electric force between them becomes zero.
Reason (R): Reduction in a force due to introduced material is inversely proportional to its dielectric constant.
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Answer

  1. Both A and R are true, and R is the correct explanation of A.

Explanation:

The dielectric constant of any material is $\text{K}=\frac{\text{E}_0}{\text{E}}=\frac{\frac{\text{F}_0}{\text{q}}}{\frac{\text{F}}{\text{q}}}=\frac{\text{F}_0}{\text{F}}$

$\Rightarrow\text{F}=\frac{\text{F}_0}{\text{K}},$ where F0 is force when conductor is not present between the charge. Fis a force after introduction of conductor between charges. Since dielectric constant of a conducting medium is infinity therefore F = 0.

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