Why is oil drop used in Millikan's oil drop experiment instead of water drop?
The oil drop experiment was an experiment performed by Robert Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). For his experiment Millikan used very tiny oil droplets (due to its low evaporation rate). Earlier, J.J.Thomson attempted an experiment where he observed the behavior of falling charged water drops. This experiment, however, was inaccurate because the water drops evaporated during the experiment, and Thomson could only estimate how fast they evaporated in order to interpret the results. In 1909 Millikan performed an experiment based on an Thomson's attempt, but used charged oil drops instead of charged water drops. This eliminated the evaporation problem and considerably reduced the uncertainty of the experiment.&