alleryCoulomb's law in vacuum is F = (1/4πε₀)(q₁q₂/r²). The value of 1/4πε₀ is approximately:
A8.85 × 10⁻¹² N m² C⁻²
B9 × 10⁹ N m² C⁻²
C1.6 × 10⁻¹⁹ N m² C⁻²
D6.022 × 10²³
Answer & Solution
Correct answer: B. 9 × 10⁹ N m² C⁻²
**k = 1/(4πε₀) ≈ 9 × 10⁹ N m²/C²** (in vacuum).
ε₀ = 8.854 × 10⁻¹² C²/(N m²) is the permittivity of free space.
In a medium, replace ε₀ by ε = ε₀ × ε_r (relative permittivity / dielectric constant).
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