6
1.
THE CHARGE OF THE ELECTRON
d is the distance in centimeters between the inside faces of the
plates, 0 is the density of the oil, 77 is the coefcient of viscosity of
air (0.000182 at 23° C.), g is the acceleration
of grav1ty rn centimeters per
second per second, & = 0.000167, }) is the bar-ornetrrc
pressure
of the gas
in centimeters of mercury, al is the
mate radius of the drop in centimeters as given by equation l—-8,
vd is the velocity of free fall of the drop in centimeters per second,
au is the velocity of rise under the opposing forces of the electrical
eld and gravity and V is the potential difference in volts between
the two plates.
The charge gained or lost by a drop (A6), may be calculated
from equation 1—13. Thus
Ae = k1/e2
(1—14)
where Az; is the difference between two upward velocities.
The value of e,. was found by Millikan to be an integral multiple
of
€ = 4.770 X 10’10 e.s.u. (i0.005)
=
1.590 >< 10“19 coulombs.
1—4.
Comparison With the X—ray Value—For a number of
years, the value € = 4.770 X 10*10 e.s.u. has been accepted as
the most accurate known.
Later, an X—ray method, to be described
at the end of this chapter, has yielded a value of @ differing from
the oil-drop value by an amount appreciably greater than the
experimental errors in either of the two methods.
Many attempts
have been made to determine the cause of this discrepancy.
For
example, the coefcient of viscosity of the air has been redetermined by Kellstrôm 2 who has found 77 to be equal to 0.0001835
at 23° C.
With this new value, the oil-drop method gives
@ =
(4.818 =}: 0.012) >< 10—10 e.s.u.
in closer agreement with the X-ray value of € = 4.803 >< 1010 e.s.u.
Bond2 has also found n(at 23° C.) to be 00001834. On the other
hand, Ishida and others 2 have repeated the oil—drop experiment
and, using the old value of 77, have found
; = 4.806 X 10—10 e.s.u.
1.
THE CHARGE OF THE ELECTRON
d is the distance in centimeters between the inside faces of the
plates, 0 is the density of the oil, 77 is the coefcient of viscosity of
air (0.000182 at 23° C.), g is the acceleration
of grav1ty rn centimeters per
second per second, & = 0.000167, }) is the bar-ornetrrc
pressure
of the gas
in centimeters of mercury, al is the
mate radius of the drop in centimeters as given by equation l—-8,
vd is the velocity of free fall of the drop in centimeters per second,
au is the velocity of rise under the opposing forces of the electrical
eld and gravity and V is the potential difference in volts between
the two plates.
The charge gained or lost by a drop (A6), may be calculated
from equation 1—13. Thus
Ae = k1/e2
(1—14)
where Az; is the difference between two upward velocities.
The value of e,. was found by Millikan to be an integral multiple
of
€ = 4.770 X 10’10 e.s.u. (i0.005)
=
1.590 >< 10“19 coulombs.
1—4.
Comparison With the X—ray Value—For a number of
years, the value € = 4.770 X 10*10 e.s.u. has been accepted as
the most accurate known.
Later, an X—ray method, to be described
at the end of this chapter, has yielded a value of @ differing from
the oil-drop value by an amount appreciably greater than the
experimental errors in either of the two methods.
Many attempts
have been made to determine the cause of this discrepancy.
For
example, the coefcient of viscosity of the air has been redetermined by Kellstrôm 2 who has found 77 to be equal to 0.0001835
at 23° C.
With this new value, the oil-drop method gives
@ =
(4.818 =}: 0.012) >< 10—10 e.s.u.
in closer agreement with the X-ray value of € = 4.803 >< 1010 e.s.u.
Bond2 has also found n(at 23° C.) to be 00001834. On the other
hand, Ishida and others 2 have repeated the oil—drop experiment
and, using the old value of 77, have found
; = 4.806 X 10—10 e.s.u.