Hangmen - Charged Balls in Different Media · Physics Brawl 2012 #FoL.2
Physics · electromagnetism
Problem
There are two balls of mass m and electric charge q (with the same sign) hanging from two slings of length l fixed in the same point. These balls are placed in air with density ϱₐ = 1.2 kg·m⁻³. Due to the electric repulsion of the balls, the slings are forming an angle α. If we put the same aparate in the olive oil with relative permitivity εᵣ = 3 and density ϱₒ = 900 kg·m⁻³, the angle will remain the same. Consider the permitivity of the air to be same as permitivity of vacuum. What is the density of the balls?