Falling raindrops frequently develop electric charges. Does this create noticeable forces between the droplets? Suppose two 1.8 mg drops each have a charge of + 29 pC. The centers of the droplets are at the same height and 0.36 cm apart.

F = 5.83 10⁻¹⁷ N

Explanation:

The electric force is given by

F = k q₁ q₂ / r²

With Gauss's law electric field flow is equal to the charge inside the Gaussian surface, if we make a spherical surface around each drop, the force independent of small deformations due to air resistance

q₁ = q₂

F = 8.99 10⁹ (29 10⁻¹²) ² / (0.36 10⁻²) ²

F = 5.83 10⁻¹⁷ N

As the two drops have a charge of the same sign they repel