An infinite line of charge has a linear charge density of $10^{-7} C m^{-1}$. The magnitude of the force acting on a charge $6.4 × 10^{-19} C$ kept at a distance of 8 cm from the line of charge is

$1.44 × 10^{-14} N$

The correct answer is Option (4) → $1.44 × 10^{-14} N$

Substituting values:

E = (9 × 10⁹ / 2π) × (10⁻⁷ / 0.08)

E = (9 × 10⁹ × 10⁻⁷) / (0.16π)

E = (9 × 10²) / (0.16π)

E ≈ 2.25 × 10⁴ N/C

Force on the charge:

F = qE

F = 6.4 × 10⁻¹⁹ × 2.25 × 10⁴

F = 1.44 × 10⁻¹⁴ N