Two similar point charges $$q1$$ and $$q2$$ are placed at a distance r apart in air. Assume that a slab of thickness one third the separation between the charges is placed between the charges and it is observed that the ratio of Coulomb’s repulsive force before and after placement of dielectric is $$25$$:$$9$$. Then the dielectric constant K of such a slab is

Question

Two similar point charges $$q1$$ and $$q2$$ are placed at a distance r apart in air.  Assume that a slab of thickness one third the separation between the charges is placed between the charges and it is observed that the ratio of Coulomb’s repulsive force before and after placement of dielectric is $$25$$:$$9$$. Then the dielectric constant K of such a slab is

Infinity Learn · Accepted Answer

$$F1=q1q2d214$$πεoIn the second case effective $$distance2d3+kd3F2=14$$$$π$$$$Eoq1q22d3+kd32F1F2=2.59=q1q2/d2q1q2/2d3+kd322.59=2d3+kd32d2=53=23+k133=kK=9$$

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