Solving a problem in physics section 71 point 22 electr

22. A drop of oil, negatively charged, is placed between the plates of a horizontally located flat capacitor. The electrostatic field strength is selected so that the droplet is at rest. Determine the droplet charge if the potential difference between the capacitor plates is U = 500 V, the distance between the plates is d = 0.50 cm, the droplet radius is r = 7.6 ∙ 10−5 cm, and the oil density is ρ = 0.90 ∙ 103 kg / m3 .