In 1909, Robert Millikan performed an experiment to determine the fundamental ch
ID: 2236854 • Letter: I
Question
In 1909, Robert Millikan performed an experiment to determine the fundamental charge, e. This experiment involved levitating a small oil drop in an electric field. A purely fictional descendant of Millikan decides to do a repeat experiment with a twist. After watching a YouTube video of some crazy scientists levitating a frog with a magnetic field, he decides to try it with his ancestor's setup. He decides to use a squirrel with a mass of 0.75 kg. Note: This is a really BAD idea. The apparatus consists of a horizontal metal plate that can be charged to give a constant electric field above the plate. He charges it up to give an electric field of E = 5000 N/C pointing straight up. How much electric charge and what sign of electric charge must be put on the squirrel so that it levitates above the plate? Note: levitate means static equilibrium between the electric force and the squirrel's weight.Explanation / Answer
to levitate F electirc - mg = 0
q E = m g
q = mg/E positive since E points up
q = 0.75*9.81/5000=0.0014715 C