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If F is the force between two point charges submerged in a medium of dielectric constant K, then on withdrawing the medium, the force between the charges becomes

Asked in GUJCET 2013 · Coulomb's law and superposition

Answer: (2) FK

Step-by-step solution

Idea: a medium of dielectric constant K reduces the Coulomb force by the factor K.

In the medium: F=1/(4πε₀K)(q₁q₂)/(r²)

Medium withdrawn (vacuum): F₀=1/(4πε₀)(q₁q₂)/(r²)

(F₀)/F=K, so F₀=FK.

The force increases, because the medium's induced charges no longer screen the two charges from each other.

Why the other options are wrong

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