When two charges are placed in water then the Coulomb force between them reduces to _____________?
Correct answer: C. 1/78 times
- A. 1/2 times
- B. 1/3 times
- C. 1/78 times
- D. 1/58 times
Explanation
In a medium, Coulomb force becomes Fmedium = Fair/εr; water has a relative permittivity of about 78, so Fwater ≈ Fair/78, or 1/78 times the force in air. The likely mistake is 1/2 times, which does not use water's dielectric constant.
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About Coulomb's Law
Coulomb's law gives the electrostatic force between two point charges in terms of their magnitudes, separation and the medium between them. Questions involve attraction and repulsion, the inverse square relationship, superposition of forces and vector direction, which must not be confused with the electric field produced by a charge.
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