30
2.
_
THE MASS OF THE ELECTRON
then draw them back from C.
Their velocity ?) is then equal to
the distance ! (=r0, where 6 is in radians) divi_ded by nT, or
7)
; ïÎ
:
ΑÏ
,
(2—14)
»
-
nT
n
'
where f is the frequency of the oscillator. Together with equation
'
2—1, this leads to the relation
—
9f
e/m _
,
(2 15)
One may vary
the magnetic eld strength instead of
the frequency
of the oscillator and observe the critical value of H for which the
galvanometer current clips sharply to zero. This is a precision
method and has given the value 8
e/m = 1.7597 X 107 e.m.u./g.
The accuracy
in this method (:0.0004 X 107) depends almost
solely on the measurement of H, the eld strength, since f, the
frequency, is known to at least one part
in a million (crystal con—
trolled oscill‘ators are u'sed), @ is an integer and 9 is an angle which
can bé determined very accurately from measurements on
the
apparatus With built-in microscopes. It is to be noted that the
radius r does not enter into the nal equation,
—'
2—8.
The Magnetron of Hull.—À two—electrode vacuum tube,
'
which consists of a hot lament strètched along the axis of a cylinë
driCal anode, is placed in _asolenôidor between the poles of an
electromagnet in such a manner that the magnetic lines of force
‘
are parallelto the lament. The ow of electrons
la',
ment
anode constitutes an electric current which fnay
mdby m of:-ga miniamm_eter connected inÏ series With the"
anodebatterÿThls current
Constant" à.S
.
?; eîdstrengthrsmcreasedfrom zerogjun‘tn
(
'
%
When 1tS“denïÿdmpstozem
that the
*
an©d€PO‘Cëü‘ïlaladth€lamenttemperatureremam Ï:Çônstants
.
°nean0ther
2.
_
THE MASS OF THE ELECTRON
then draw them back from C.
Their velocity ?) is then equal to
the distance ! (=r0, where 6 is in radians) divi_ded by nT, or
7)
; ïÎ
:
ΑÏ
,
(2—14)
»
-
nT
n
'
where f is the frequency of the oscillator. Together with equation
'
2—1, this leads to the relation
—
9f
e/m _
,
(2 15)
One may vary
the magnetic eld strength instead of
the frequency
of the oscillator and observe the critical value of H for which the
galvanometer current clips sharply to zero. This is a precision
method and has given the value 8
e/m = 1.7597 X 107 e.m.u./g.
The accuracy
in this method (:0.0004 X 107) depends almost
solely on the measurement of H, the eld strength, since f, the
frequency, is known to at least one part
in a million (crystal con—
trolled oscill‘ators are u'sed), @ is an integer and 9 is an angle which
can bé determined very accurately from measurements on
the
apparatus With built-in microscopes. It is to be noted that the
radius r does not enter into the nal equation,
—'
2—8.
The Magnetron of Hull.—À two—electrode vacuum tube,
'
which consists of a hot lament strètched along the axis of a cylinë
driCal anode, is placed in _asolenôidor between the poles of an
electromagnet in such a manner that the magnetic lines of force
‘
are parallelto the lament. The ow of electrons
la',
ment
anode constitutes an electric current which fnay
mdby m of:-ga miniamm_eter connected inÏ series With the"
anodebatterÿThls current
Constant" à.S
.
?; eîdstrengthrsmcreasedfrom zerogjun‘tn
(
'
%
When 1tS“denïÿdmpstozem
that the
*
an©d€PO‘Cëü‘ïlaladth€lamenttemperatureremam Ï:Çônstants
.
°nean0ther