A small note on the Millikans Oil Drop Experiment,

Millikan's oil drop experiment is to determine the the specific charge of an electron.In this experiment Millikan used the double chambered instrument.In this experiment the instrument consist of the two window from one window light is passed to ionized the electron and from the next window X-ray is passe to ionize the electron if the electron is not ionized.this instrument also consist of the automiser and the clock oil bottle attached with the double walled chamber. in this experiment clock oil is used because in this experiment the liquid is used should have the high density and  not be volatile substance.in this experiment there are two plates A&B as shown in figure below.the plates A consist of a hole from which a drop of the liquid is falls from it by the help of the automizer and the plate B is connected to the electricity. similarly a small microscope is kept on it to see the every motion of the oil drop  in the double wall chamber. when the drop of the liquid is falls from the whole which is in the plate A is ionized by the lights and X-ray which are subjected in the chamber from the windows.  To find the the specific charge Millikan done this experiment on the basis of the following two condition,

millikan's oil drop experiment to determine the specific charge of an electron.

• The specific charge of an electron in the presence of the gravity only,

• The specific charge of an electron in the basis of electric field and gravity, 

1.  The specific charge of an electron on the basis of gravity only,

when the oil drop is falls under the gravitation field its velocity goes on increasing and the oil drop gets the terminal velocity Vt. Ten if F is the gravitational field,W be the weight of the oil drop,g be the gravity, r be the radius of the oil drop now mathematically it can be written as,
                                              F=