What is the charge of a 5ng droplet if it hangs in an electric field of 10 kV / m?

Initial data: m (droplet mass) = 5 ng (5 * 10 ^ -9 g; 5 * 10 ^ -12 kg); E (voltage of the electric field in which the droplet hangs) = 10 kV / m (10 * 10 ^ 3 V / m).

Reference values: g (acceleration due to gravity) ≈ 10 m / s2.

Let us express the droplet charge from the formula: E = F / q = m * g / q, whence q = m * g / E.

Calculation: q = 5 * 10 ^ -12 * 10 / (10 * 10 ^ 3) = 5 * 10 ^ -15 C (5 fC).

Answer: The droplet has a charge of 5 fC.