In 1909 Robert Millikan was the first to find the charge of an electron in his n
ID: 1393539 • Letter: I
Question
In 1909 Robert Millikan was the first to find
the charge of an electron in his now-famous
oil drop experiment. In the experiment tiny
oil drops are sprayed into a uniform electric
field between a horizontal pair of oppositely
charged plates. The drops are observed with
a magnifying eyepiece, and the electric field is
adjusted so that the upward force q E on some
negatively charged oil drops is just sufficient
to balance the downward force m g of gravity.
Millikan accurately measured the charges on
many oil drops and found the values to be
whole-number multiples of 1.6
Explanation / Answer
In the equilibrium net force acting on drop = 0
q*E - m*g = 0
q = m*g/E
= 1.56735*10^-13*9.8/(3*10^5)
= 5.12*10^-18 C <<<<<<<<<<---------------Answer