The force between two point charges placed in air is F. If air is replaced by a medium of relatives permitivityƹ , the force is reduced to
Correct answer: C. F/ƹ
- A. ƹ, F
- B. ƹ/F
- C. F/ƹ
- D. ƹ,
Explanation
Electric force in air: F = q1q2 / 4πϵor2 (where ϵo is the permitivity in air) Electric force in medium: F' F' = q1q2 / 4πϵoϵrr2 (where ϵr is the permitivity of the medium) F' / F = ( q1q2 / 4πϵoϵrr2 ) / ( q1q2 / 4πϵor2 ) F' / F = 1 / ϵr F' = F / ϵr
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