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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Electrostatics describes forces between charges through Coulomb's law, electric fields and field intensity, then uses electric potential to measure energy per unit charge. Capacitors store charge and electrical energy, with capacitance depending on geometry and dielectric material, not simply on the amount of charge present.
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