28
'
2.
THE MASS OF THE ELECTRON
In
of
and also Perry and Chafïee,7 precision
results have been obtained. Thus
'
e/m
=' 1.760 X 107 e.m.u./g.,
‘
to within :0.0025 X 107.
2—5.
Units of Energy, Velocity and Momentum.—The energy
of a moving charged particle may be expressed in a variety of ways.
As is well known, the kinetic energy of a particle of mass m (grams)
.
_
and velocity @ (centimet‘ers per second) is m02/2 ergs. Instead of
expressing the energy in
it is common practice today to state
its value in electron-volts, (abbreviated e.v.).
-
One electron-volt is the energy which an electron acquires
_
when accelerated by a potential difference of one volt.
The conversion from ergsj @Î
V, or vice versa,
"
>
is'made by means of the equation
_
‘
é”= %mv2 = 108%»… =
%
(2—12)
where 6… is the charge of the particle in electro—magnetic units and
.
es is the charge inf electro—static units. The factors 108 and 300
',
are used to convert from volts to e.m.u. and e.s.ü., respectively.
D‘As an example, ”an electron, accelerated from rest‘by a positively
"
"
charged metal plate whose potential is one—hundred » volts
). (V= 100), will have
‘âof1.591 >< 10—10 ergs or 100 e.v.'
'
when it
the plate. Thus, one electron-volt is equivalent
“IS 3180 Cômmo… pract1œ today to referto thevelomtyofa
_
":
: terms efthe acceleratingvgltageneededto
_
_
—
fheknown°hafge andmassvalues1tmaybeshownthatone
efse°@n@landanalhapartmleavel@CltY@f-‘978X15œntl
attheen@fthlsb@®k
'
2.
THE MASS OF THE ELECTRON
In
of
and also Perry and Chafïee,7 precision
results have been obtained. Thus
'
e/m
=' 1.760 X 107 e.m.u./g.,
‘
to within :0.0025 X 107.
2—5.
Units of Energy, Velocity and Momentum.—The energy
of a moving charged particle may be expressed in a variety of ways.
As is well known, the kinetic energy of a particle of mass m (grams)
.
_
and velocity @ (centimet‘ers per second) is m02/2 ergs. Instead of
expressing the energy in
it is common practice today to state
its value in electron-volts, (abbreviated e.v.).
-
One electron-volt is the energy which an electron acquires
_
when accelerated by a potential difference of one volt.
The conversion from ergsj @Î
V, or vice versa,
"
>
is'made by means of the equation
_
‘
é”= %mv2 = 108%»… =
%
(2—12)
where 6… is the charge of the particle in electro—magnetic units and
.
es is the charge inf electro—static units. The factors 108 and 300
',
are used to convert from volts to e.m.u. and e.s.ü., respectively.
D‘As an example, ”an electron, accelerated from rest‘by a positively
"
"
charged metal plate whose potential is one—hundred » volts
). (V= 100), will have
‘âof1.591 >< 10—10 ergs or 100 e.v.'
'
when it
the plate. Thus, one electron-volt is equivalent
“IS 3180 Cômmo… pract1œ today to referto thevelomtyofa
_
":
: terms efthe acceleratingvgltageneededto
_
_
—
fheknown°hafge andmassvalues1tmaybeshownthatone
efse°@n@landanalhapartmleavel@CltY@f-‘978X15œntl
attheen@fthlsb@®k