Question

2) Three identical metal spheres are supported on insulating stands and are all neutral at the start of the experiment. Then: sphere 2 makes contact with sphere 1 while sphere 1 is close to a charged plexiglass rod. Contact is then broken with the rod in place. Sphere 2 touches sphere 3 and both spheres are taken to another part of the lab where the force between them is measured to be 0.002 N when their centers are 10 cm apart. They're not touching anymore. e . a) Determine the amount and sign of the charge on sphere 1. Briefly explain the reasoning (not the algebra) behind your calculation and result. b) Consider a system consisting of sphere 1 and either (but not both) of the other two spheres after they have touched. Is the net charge of this system like the rod, unlike the rod or neutral? Explain your reasoning

Answer 1

As shown in fig sphere 1 has -ve charge on left due to attraction from Rod & hence on sphere 2 charge is as shown due to inductance. now F = k q_1 q_2/r^2 Because q (+ ve) on 2 = q (- ve) on 3 Therefore q_1 = q_2 = q = > k q^2/r^2 = F = .002 = > q^2 = .002 times r^2/k q = r squareroot .002/k = 4.7148 times 10^- 8 c q (-ve on 3) = 4.7148 times 10^- 8 c (b) Net change will be equal because after touching they will be neutralize.