Question

1. A small droplet of oil with a mass of 2.00 x 10-15 kg is given a small excess charge and is then held suspended in a region of uniform electric field directed upward with a magnitude of 6125 N/C. a) Is the excess charge positive or negative? b) How many elementary charges (unbalanced electrons or protons) are on the oil droplet? Note: this is the famous Millikan Oil Drop Experiment. Millikan took into account the air friction and buoyancy on a droplet (which we ignore here) and solved for the total charge on the drop. By finding that the charges on many droplets were multiples of a single common value, he was able to experimentally find the charge on a single elementary charge for the first time. He won the Nobel Prize for that accomplishment. We will duplicate his experiment in a future lab: we will not be getting Nobel Prizes.] 0 2

Answer 1

Thanks give positive rating

Eq = mg q = mg/E = 2 times 10^-15 kg times 9.8 m/s^2/6125 N/c = 3.2 times 10^-18 coulomb charge on the drop should be positive so, upward force is exerted by electric field charge on drop = 3.2 times 10^-8 C charge on electron/proton = plusminus 1.6 times 10^-19 coulombs eta = 3.2 times 10^-18/1.6 times 10^-19 = 20 positive charge proton