a ^íuây 6f rbe variation of the dieleotric c
TRANSCRIPT
A ^íuây 6f "rbe Variation Of The Dieleotric C<»»tant Of Air With 3Pressure
By Allen Henry BurMimlter
Approval
Thesis C<Hi3nittee
Â_ Study Of The Variaticm Of The Dieleotric Constant Of Air With Pressure
By Allen ^nry Borldialter
Submitted In psrtial fulfilment of the requirenfônts for the degree of Llnster of Science of the Gradua te School of the Texas Tectaoloplcal College^ 1934.
\E TEXAS TECHNOLOGICAL COLLEGE LIBÍARV I n D o n n u TCVAe
fi^i^C-OiJgl
lastorical AC ^ The first kna»n deteinnination of the
-Xj dieleotric constant of alr yjns porfonned by
^^^^ Boltzmanni lEs method consisted of placlng a
^^ known clmrgo on an air condenser and noting the
change in potentlal as the ccMidenser was evac-
uated. Hls value for the dieleotric constant
of alr was 1.000590 at 760 mm» and O degrees
C^Eitigrade. The next work rms done by Ayerton Z
and Porry in 1877. They comxjared the capecity
of a knc«m címdenser c<»itaining alr v/l th tbat
of the san^ condenser evacuated. They ma de
their readings with a quadrant electrometer and
secured 1.0015 which, however, Is now generally 3
relected. The next work was done by Klenienclc in 1885. He measured the change in the capacity
of an air ccmdenser at normal pressure and then VV/ICT?
evacuated. The values of the cbarge were nieasxu»eà
by discliarging t^e cmidenser through a t alva lor:-
eter. The niean of his best values ^ives the
dieleotric constant of air to be 1.000581. TJhtil
this time ali measuren^nts lind been r-nãe vmder
unidirectional c<»iditÍons. ileraencle clnrged
l.I.Boltzamnn. lien Berichte 69, Part 2, 795,(1874) 2.Carman and iTubbard, PTi-s. '^ev.,29, 299, (1027) S.I.KlenKjncic. ilen ;lerlcbte Bd. 91»
hls condenser 60 tinfôs per second but alwajrs in
the B&me dlrection.
I%ny of the more reoent determinatlons have
been msde at radio frequency» It seenas t!at the
so-called heterodyne or "beat" method vma devei-
oped by Hyslop and Camsin but was first used by 5-
Gill. This method makes use of the change In tbe
frequency of an osclllatlng elrcuit caused by a
small change in the cai icity of the condenser.
The effect Is observed by coupllng the circuit
under test with another osclllator of nearly the
same frequenoy. xhe frequency of the reference
osclllator Is assuined to stay constant and the
other frequency to be tuned to it»
0111's oscillators were placed some distance
apart but were rather closely coupled to the
deteotion systei •. The range of Inaud 1 blllty near
2ero boat was too broad for great áccurac;/ but a
series of clleks were notlced near tdc cd^e of
the Inaud/' ble imnge. Clll made his readlifS to
these assuming tbat they alv/ays occurred in tde
same plece. ris test condenser uns nn ívli' condens
er under n bell Jar in parallel with a precla:'Oi
condenser outside. After ad ittlng tbe alv^the
4.ryslop and Carimn, P ys. " ev., 15, 243,(1920) 5.nill, " ad. ev., 450, (1921)
precision condenser ^ms tuned untll the olicks
were again heard. ílls values for the dlelectric
constant of air were as follows.
920 meters* — 326 E.C«- —1.000658 1300 meters 230.5 E.C. ^-1.000654 1760 meters—^ 170.5 K.G. -1.000654 4í)00 meters—™—75 K.C.——1.000653
He elaims an aecuraoy of 1% of (K-l) and
assumes that the2»e is no ehange with frequency,
altlKJugh hls values are imioh higher than those
for unidirectional ccaiditlons.
Fritts^used a sindlar method for the deter-
minatlon of tbe dlelectric constant of seve 'ai
gases, among them air. lie increased the aecuraoy
of the heterc^yne method by allowlng tbe oscilla
tors to interfere et an aud i ble frequency. Sb-is
frequency vma recorded on a photographl.c film
where it eould bc compared with the trace of a
standard tunlng fork. From the chan e in the
frequency it was posslble to calculate the
change ?.n capacity and t':en tbe dlelectric co stant
of the (-as under test. IIls determinatlons glve
1.000540 for air at 500 K.C.
6.Fritts, Phys. ev», 23, 345, (1924)
4
Zahn* B&de another modification of the same
systom. He improved the system by tunlng the
Intorference note to a knov.n audlo frequency.
lUs oompensation was rmáe by a ^r*eclsion condens
er shunted by a largo fixed condenser and in
series with the test condenser. The advantage of
this arrangeroent was the cmltiplying factor or
the fact that a si mll change in the test ccmdenser
was aco^Bipanied by a large cbnnge in the precision
ccmdenser. lüs value for the dlelectric constant
of air was l.(X)0S72 at 10(X) K.C. and under standard
conditlons. Be elaims an accuracy of If» for tbe
decimal part of the dlelectric constant. It is
interesting to note tbat Pritts also elaims an
accxiracy of one part in 540 or l/S of ifo vriile
his values and Zalm's differ by 7}U
dock'' also made use of the bete-^odyne method.
He superimposed bis beat note on a 1000 ci clo
source and tuned for zero beat between these two.
\Vhen air was admitted balnncc was restored by the
same n^thod as used by Zaim. Rock glves for his
value of the dlelectric constant of alr 1.000578
at 200 K.C»
Carrnn and I^blmrd cnll attentlon to f-^c
7^''nhn, P^ys. '^ev., iJ4, 400, (1024) e .^ock, Doctorate D i s s e r t a t l o n , Cat^. ün iv . of
America. (1927) 9.Carman and llubbard, Fhys. dev. 29 , 299, (1927)
•'dct t-^nt t ^e v?».l eo of Fsdttc? fí -:d M n n:H> iiie':
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8
that every elen^nt of volume dV possesses an
oleotrlc m<»nent IdV, I belng the electrlc
cKnnent per unit voltane»
If a cylindrlcnl cavlty of very small
cross sectlon, but of flnite length, is cut out
of an Insulator parallel to the Unes of force,
a unit electrlc charge brought Into the cavlty
will be acted on by a force E, ?/Mch is Imown
as tTe electrlc Intenslty. If now a sectlon be
cut out bet?/een two parallel planes very elose
together and perpendlcul^^ to the Unes of force,
a unit electrlc cba :ge broupl t Into the sectlon
will be acted on b ^ a force B, v;bic> is greater
tban E by tde amount 4WI. It then follows thnt
D-E-^4r^I (1)
The classical tbeo->y of dlelectric constants
; Ives the following relations.
K = D , Et4TrI
"ü W K = 1 •t-4TT'I
In the case of n vr cinir^ D s " and lie^-^.ce D
o' K i s equal t o 1 .
I f nov t ' e molccule^ of n d l e l e c t r i c a re
placed betv/een conductlng p i a t e s id^ic"! a re lnr£e
in comi)arlson ivlth tbe d i s tance betv/een t'^e>n, a
bomogeneous f l e l d i s estndli.^becl In t'^e cHclecti Ic
?;^en t^^e plí^tes a r e unlforr l y c^^nvi^cá v l t h
9
a surface density r-. If the actual eleotrlc
intenslty acting upon a single molecule is F^
the molecule would have Induced upon it a moment
given by the following relatlon.
m-*iP (2)
where «,ls the polarizabllity of the molecule.
F may be better understood by supposlng a
unit positive charge in the médium to be enclosed
by a small sphere, which is large as conqpared to
BKSlecular dimensions, but small as compared to
the <2dstance between the plates» The force
aeting ^i this unit cha- ge may now be trented ns
e<msiat±ng of three eompcaients as follows,
FsP^-hF^+Fj (3)
F, is the force due to surfftce density on tdo
plates and is equal to énrí (4)
F^ is áae to polsrizatlon of irmterlal outside
of the small sphere and is equal to t'e force due
to la7/ers of induced charge on tbe t??ite dal faclng
the plates plus the force exerted by the cbarre
on the sur/ace of the small spherlcal cavlty.
This force is èT ^ í W t e eqtmtion
F=-4/rIt4;rI (5)
Fj is tbo force áXLO to tde material cortained
in the sphere. idis cannot be obtalned In :
valld expresslon In most cases. In t-e cnse
10
of gases In which the n^lecules move independ-
ently this may be assumed equal to zero. The
ocmipleto expresslon fop the imlue of F then
becomes ,
F^4n^-4nl t4/rl
According t o t h e ftaidastôntal law of
e l e c t r o s t a t l c s , D =4'n'tf^ i t fo l lows frcan (1)
t h a t 4TTVirB+4wI and ccmsequen t ly ,
F = E + 4TTI (6)
The Claussius-dossottl exjmesslon is
arrived at as follows. The electrlc moment
per unit volume is given by the relatlon
I = nm = n g*., ( ">• irl).
Fr^n equation (1) the following relatlon
is secured*
| ^ = ^CH+im^). (V)
By s o l v l n g t h e above r e l a t l o n and r e p l a c l n '•^L
D by K t b e fc l lov; ing r e l a t i o n i s s e c r r e ' .
K-1 ^ 4nn ^ (r )
Slnee i n P. purê subs tonce n _ F d _ , vd ore TT i s
Avogadro 's nttmber, d I s td^e d e n s i t y , r ^d M I s V^e
molecu la r r e l g ^ t , t h e above e x p r e s s l o n bocoires
K - 1 . 4trT7^ (9)
íbis is nov set cauf^l to P n.nd cplled
r- olar polarlzatlor. :"nce K Is a purê nu ber
11
and !' is a molar volume then P and K have
dlmeaslons of volume. By dividlng equation (9)
by }l the classical Clausslus- ossottl equntlon
Is secured.
K-1.1^47rI^ (10)
Slnce the value of IJ-2 is so nearly equal
to 3 for such a gas as alr ean^tlon (10) r ay be
written jC-1, 4frd ç^ and still be norc acctírote
than any experimental method for fIndlng tbe value
€f ^ 1 .
I f t be above equation I s lüul t lp l led by "d"
i t becomes K-1 =d.4iyl« • Prorn t h i s i t i s
apparent tl^at tbe value of K-1 i s p ropor t lona l t o
f'^e dens i ty of the rns T/dicb I s in tu rn propoi'
t l o n a l t o the pressure l i rr^e teiripeinture i^eimlns
c o n s t a n t . I f the value of t^e te^^ i 4TT"d»i i s
c o n s t a n t , v/ ich i s t^e usu?3l nss-iüTptlon, f^er*
the value of K-1 i s propor t lonnl t o t^e p r e s s n r e .
I t i s f-e purpose of t b i s e:>perlrnont t o c'^eck
tbe r e l a t l o n betv/een K-1 and t ' :e pressnre Of a^ r .
12
The Experimental !;etbod
The method used in t h i s experlment I s tbe
v/ell known heterodyne method in wbicb the beat
between two r a d i o fx*equency o s c i l l a t o r s can be
olMerved on the screen of a catbode r ay t u b e .
Tbe method of compensa t i on for cbanges in V-^e
c^pnclty of tbe t e s t condenser i s V' n r^e^^les
arrangeroent of condensers as Introduced by ' n rd
in 1924.
Tbe reference o s c l l l a t o r i s n General ^'adio
/> lezo-e lec t r ic u n i t operat ing a t approximately
B30 k i l o c y c l e s . T^e c i r c u i t v&ic"-^ includes t>>e
t e s t condenser T nhes use of ti^e d:rr>atron o s c l l l n t o r
uslríT a sc reen-gr i d t u b e . """ e c'^matron osc l l l a t .o r
oper-í^tes õue t o t ' e neí Gt;'ve reslsta^^ce^ c i ía r^c ter -
i s t i c of the p l a t e c l r c r i t r'--Gn placed p.t a Icwer
p o t e n t l a l t'a^^ Vmt of t ' e screen g r l d . ' be Idea
of usingdiri o s c l l l a t o r of t^e ne^r^tlve r e s l s t a n c e
c"!>f!racterlstic v/as sii-gesterl iv^ tbe v ork of
Pí i i rs to in 1920, V7' e: e"r? de vüel an e l e c t r i c
nrc t o sup^)ly po?/er t o a '-v •? frequericy o r c i l l ' ^ t o - .
i:'''As oscill^^tor» Tf\3 iiced as n r-iennn cf ec-c.n *n.:
t ' e d l f f l c u l t l e s cf tcn eiicoimte-f^ei i r • ^o use of
t be rove fatr:ilinr types of o s c l l l n t o r s . In theíje
l .See pOcG 4 . d . l o r e c r o f t , "Electron lubes l pp .:e 42^, (ldv'3) 3 .Conduct ivÍ ty a d D i e l . Con^t. of ^delectr^ies
At dlfb Freoue^ieies. ^n- ' r s to , Koyii Soe. Proc. 9^^. pp r^^3-. Pd, 7nr . 2 , (102n)
13
types of osclllntors It is necessary to have
a coupllng coll for regenerrtlon. The dlstributed
capacity of tbls coll bns t^e effect of detimlng
tbe oscillatory circuit from tbo natural period
of that circuit alone. Slnce the ^rld-plate
capacity of the tube Is In series with tbe
dlstributed capacltles of both these colls a
snmll change in tbe relative posltion of t' e
electrodes due to beatlng of t^e tube vould
cause an increased chantre In the frequency of
osclll^tlon of tbe reson-nt clrenlt. *>'ls
dlfflculty Is rinlmised " y tbe use of tde
dynetron osclll' tor slnce in t' is circuit the
inter-electrode c p clty "s i^ par^llel^ vdth
tde cnpacity of tbe reson^nt ei^crit. ty. lc-íl
ebMpn<5te" istle curve of the tube used "n tbls
oscillí"tor "s s''-ovn *n flt ^ e 1.
It •111 ix:' noticed t ':t -etwee - t'ie pc nts
^ú^ Brd "b" ^Iccperse of plote volt ige is
pccomp'^nied iv^ ^n i^crense of t' e pl^te cii''re t.
''bis glves p negíitive reslstance c^rnrrcteidstlc.
As cnn be seen fro " figtire 1 tbe resistr^nce
sectired by t king t- c slope of f e cdí- r- rter st • o
curve ne r f -e n dpolnt of the cdr. ndc p^rt
figures to be -47,300 o'rs. If an c ectvlc-lly
4.0i-ecroft "Electron "udes; Page -29, (19rd>)
14
resonint circuit of * reslstance equal to or
greater than this is connected In the plate
circuit of this tube it will oscillate at very
near Its ov/n natural frequency. fírch a circuit
is shovm in figure "2". Slnce, as already
expiained, f^la circuit is unusu?ílly free from
radical changes In frequency due to variations
in tbe vacuuiP tube chnracteristics it is ide l
for this wo2»k. xlie cntbode ray tube is used .s
an indicator for zero beat between tbe tv/o
oscillators. dhe accuracy of adjusting tde
frequency by this method is so great as to
'ntroduce only a negligible evpor In the restilts.
It vas necessai^y to use nn Ofrpllfier afte^
eac^ of tbe oscillators ir o" der to opera te V e
cotbode ray tube. The rmpl-fier for tl e reference
osclllator iiiakes use of c. *32 screen- i'!d tube
and ia inductlvely eoupled to tbo oselllftop.
dbe auplifler for the test circuit mal ca ise of
a 201-a tube and securee its inoiit voltrge frei
tbe drop across a 500 ohm reslstor :ín t-e screer-
pid clrciit of the osclllator. Eae' of ti-e
osclllsto 'r> with its ampllfler is enclosed in r-
sbeet .notai box €cv the pui pose of G' lelding.
The test condenser is a deneral índio
c<»idenser of 5Z0/Jjjf capacity, enclosed in n deli
jar so that It coi ld Ic eveeuí^ted. ' be compensa olon
15
for changes In this capacity durlng evacuatlon
vms acc<»nplished by the use of a General Fadlo
precision condenser of ISOOf f shiinted by a
ml ca condenser of eOOOj juf capacity. ' he air used
was drled by passlng it tbrough calciu>i cblorlde.
A complete circuit diagram of t^e apparaius used
In this experir::ent Is shown in figu e 3.
16
The Experlment
The two oscillators were started sometlme
before it was deslred to take readings so tbat
the electrodes might reach o constnnt tercperature.
Several readings of zero beat v/cre made betveen
the two oscillators imtll it Wf s certa in tbat
the one contalnlig the test condenser iv s hold!nr;
a constant frequency.
Tbe npparatuo was then read r for readings
to be made. Headlngs cf tbe preolslon condenser
were made at pressure intervala of nbout fci r
centlm ters as the bell jar was evacuated.
The follov/ing precautlons ivere taken to
prevent frequency drift durlng the tiro of
taklng readings. (1) A heating elerent v/r-s
operated in enc' of the shield boxes to maintain
a const^mt te'perrtir^e. T^.e '-'enters were con-
trollod by tbermostats vd icb nllc.ed a cbanr e
of less than .01 d gree Gentlgrade. (2) ' be
osclllator coll of t'c test oscillatci^ v/ns
enclosed in a glass jar to prevent the effoct
of bri Idity cb-onges nnd sudden cbengoa of
temperatiire. (3) '11 leads v/ere runãe r»s near-ly
rlgid as pessi^^le. (4) Tbe sbleld boxes vere
reenforced to insure rl[j;iàity. (5) Very Ic:-le
coupling \.as used to take voltpge off f:.on ti e
test osclllator.
17
Data and Hesults
As tbe change brought aboat by evacuating
the bell jar is compensated for by a change In
the precision cundenser the capacity of the
circuit is the sa.ae as before. Tbe refere the
following relatlon ia true.
Solvlng for AC glves
,A C * , r/bere (IC'H•(J'"t^^e)hC' + (C*fC'M•
C is the total capacity of tb.e test co idenser,
C* is the capacity of the precision co:.der ser,
C^ is the capacity of tbe large riloa condenser
shuntlng the precision condenser. Ar. and AC^ ore
changes In the test condense;: fina in the p?''eclr,Íon
condenser respectively»
Applylng the appx^oxln^tion used by ZP'"i* tbe
above eqi,ií tion becovr.es
Tbe capacltles used in t' is calculntion •
vjcc mensv,-^'Qc at 1000 cyclrs by t> e i'se o'' t- e
rcneral H^dlo Capncltance Irid^-e. Tbe valve of
âC^ v;as the v^lue read on t'e prcc: sÍo coide- cer
necessary to brlTig the frequency bacb to t c
initif l value. Tbo value of (K-1), i/nc e • is
l.Zabn, PT ys. ' ev., 345, (1924)
18
tbe dlelectric constant, was then calculated by
dividlng AC by C^, where 0^ is the value of tbe
capacity afuctcd by a cbange in pressure. Tbe
value of Co v;ns found by replaclng tbe test
condenser by tbe supports ^emoveã from an
Identlcal condenser and rneasuring f e capacity
of these and tbe leads by t^e use of tbe beterod^nie
method. This value v/as tben subtracted f o:- 'be
measured value of n. ' -e rerrelndep vnB tben the
capacity affectod by a chf>nge cf pressure of tbe
dlelectrlr'.
Tbe follcvin;" is a sr -rple cnlci:-l"'tion
using t' e õota secui ed in this experlment.
C = 530/'/^ C =510.a A K C'= 485.4//>uf C** = 6000/7^ nC'=36.4//^
/ 530 \ 3f.4 --.2343v/L>f AC= -
K-1 - .2 -43 - .000459 510 .B
Curves v;ere tben plotted bctv/eer í>l
as ordlnates and pressure in CÍTU of r-e-cu-
as nbscissa. 'ibesa cu- ves may be seei in
figures 4 to 11 inclusive.
19
Table I
dun vi
Pres sure (K-1)19^
3.86 cm.- - - - - - 2 4 7.95 " - • - 55 11.97 " 83 15.86 " - 111 20.23 " 142 24.14 ** 171 28.02 " - 199 31.95 « - - - 226 36.27 " 255 39.84 " 279 44»37 ** . - - 311 48.42 '' 338 52.45 ** 366 56.64 ** 392 60.71 " 420 64.64 " 448 68.74 " 471
' un d2
Pressure (K-1)10^
3.a5 cm. -16 7.86 " ^46 11.84 " 79 15.76 "-^ 102 19.75 " - - - - ^ 132 23.64 *' 1-3 27.65 " 190 31.90 " ' 220 35.95 " 243 39.60 " 273 43.80 " 04 48.12 " 336 52.24 •' ooo 56.14 " -- 392 59.87 " 420 64.15 ** 442 6P.70 ' " '• 470
20
^un ríS
Pressure (K-l)lO ^
3»06 cm.- - - - - - - 20 7.08 '* 51 11»10 « - - ^ 81 15.19 ** 112 19#24 " 141 25.20 ^ 171 27.11 " 196 31.16 ^ 224 35.40 " 252 39.21 " 279 43.41 " 307 47.49 ** 334 51.43 " - - ^ 359 55.45 " dSo 69.36 " --^ 407 62.94 "* 430 68.15 " ^---4rr
Run ?'4
Pressure (K-1)10
4.9C cm.- - - - - - - 31 8.97 "" Cv 13.02 ** 91 17.17 ' - - - 119 21.14 " 149
íf 25.22 ' IYO t_ 29*17 " - - 20
o3.27 « - » --231 36.0C " snn 40.92 « - - 28r 45.15 " - - - - - - - 315 49.27 " ^ - 345 53.d5 " - ~ 3C9 57.06 '' 304 60.93 "* 419 64.91 " 442 68.82 " 4CV
21
Hun , '5
Presstire (K*l) 10^
7*92 cm.-í* - 27 13»20 ** 94 19 .11 ** 136 24 .95 ^ 178 31 .03 " 221 57 .06 " - - ^ 261 43 .08 *• 301 49 .17 " 341 Sf5»17 " 379 61.18 " 416 68 .38 " 461
^un #6
Pres s u r e (E-1)10
6.90 cm. 28 12.93 " 03 19.If^ " 139 5^5.1^ " IBO 3 1 . 0 0 " 221 36 .^n " 261 43 .04 " " 305 49 .12 « - - ^ 329 55 .30 " 385 61 .44 " - ^ 423 68.00 " 463
o 2
Run # 7
Pressure (K-l) lO^
2 .97 cm..- - - 8 6 .91 *" 45
11 .17 " 77 15 .20 " 88 19;08 " 133 2 3 . 2 4 ** 164 27 .23 " - 103 3 1 . 1 0 r" 213 S5»14 " 244 3 8 . 9 7 " 269 43 .04 "* 299 46 .94 "^ - 324 51 .19 " - - 354 55 .08 "^ 379 59 .00 *» 407 63.08 ** - - 4 3 2 68.07 " 470
Thin é8
Pressure (d-1)10^
7.Go ei-. 55 14 .01 " - 122 20 .15 " - 14d 26 .12 " 190 32 .15 " - 229 38.22 - - - - - - - 270
1 .1 .1 •--> " _ _ » ^ « _ _ ' * . ; T o
-.•*-i: . ' - j i . « » « . — — — — v-J .*: .
50.84 " - 355 56 .55 '' ^ - 405 62*42 ** - 428 ' ; ' ; . : • .w><í — — — — — — ^-v;c^.
d.-f /r;ff 4 actét-iã "if--./-c'd/ o t^ J o . r ^ ^ 4 s d l C^/é hf-ui>4. C / 3 J | X
,^ = /3S\i^á/tL
£\. r7r\V<>Ul
^ t L -.0 0 01
.4.--:i:.-^-H
% A T AÍÍAT
d.it--^$:-
:: ? .>d:tJ - -' rm-^ ^^m^
' • ^ > . ^ .
- •d-d^;
-: '>.'^^^:
=v:;.-
Circuit of A
'y pi cal üpiatron OsGÍ13-ator "m
^1,; -
^:.^
d;;--d:íS^
.*•- .'ÍJ' • •<? .
»4 M . ' V • ' « ^ ••
" -áí-^.iá í 'J : 't'd''-ífcn* V^-d-^id'
'*áSií
^ • : ^
C i r c u i t diagram cf ' ppp.-p" t u s for i.'ea:3ureTrients of d l e l e c t r i c Constairits
f^fSâ-K
u. ^^*^*^
L L -L* ] ' j t f l ' ^ J í * / J Jr i/'
, : : ? < * ^ - ,
..d.-.4^^ — ' ^ " - - í -
: > :
^/x, r/-jip
^0! tO-ft)
-_à
•díT
- -d
^0í X (/^Mi
-o^
40t Xjf/->/j
-?t:r\
^W}/tO-J^
rnz^p;
: J : V . , - Í
^::rd3
_ j - ; j
^ot y (í-M) 1 , .1
c-Já
h
sr--4
;<»/xl/-<y
34
Oonclusion
Slnee there is no consistent va 'i tion
from a straight line relation botv/een pressure
and (K-1) it is co loiderod cer tnin tbat tbls
relatlon holds. Slnce thflt conclusion is
reached the pi^ctlce of extondlng the oa.-ve to
flnd (K-1) o.t 76 > r. and 25 deg.-ecn is justified,
The values secured in this mníTiiG are t :biil: ted
belov. (K-1) 10^
5ri 530 530 530 529
527 536
J 1 ! be average of t'-=ese values ^ dve:3 5 >1.
T':is cbecks very closoly witb tbe latest values
published "j H.d.^.itson, .(l.^ao, r'nd K.L.
^?\imBvm{^7* 'die íivera,,e o" U cl* values giv-:3
530 for (K-l)l"- « Assund g tbrt t" e nve-nge of
tbeir VGl\ies and tbe voluos s - ' cd In V\'.B
experlment is t e correct VPI. c rei t-o e- -or
l3 the above results is onl: .^95 >. 'fte"
considerable study it \mQ declded t - t t-e fev;
scnttered valres neve ;' st a- red*-nle as l'or.c
v/>icb fell 30 ne^r f e nvernge. It is sugrerted
TT^Q Dlelect.- ic Cocff "cic:itc or f'-sec. .'nrt 1J7 n.E.Vatson, n.G.ir'0. n-d K.L.'-anTis-n-iy. Proc. roy. Soe. vol. 143, A850, Feb. l,a.^^>d
-tãb'
35
that the variation might be due to ioniza tion of
tbo air. This was suggested by the fact tlat
an abnormal potentlal gradient was observed
durlng the time tbat some of tbe readings were
belng mede. It is hoped that In Ve future an
investlgation of the effect of lonlzatlon of
air upc»i its dieleotric constant imy be made.
Itliough tbe expe Armnt was imsuccessful
in flndlng a consistent variation fro:r- n
straight line relrtlon between p-fessure and
(K-1), it x.üs successful in developinr nn
osclllntor r'"*ic'- is tmustiplly stable n-nâ fo
tbls reason is vc--':r desi:!:'-able or diclectT'*e
Constnnt i::en.sureiTie.Ats •
In conclusion I v/lo' to t^ank Dr. WE:. d.
Abbltt for -is asslstance and advlce tbrougbout
tbe experlt ent•
Plbllc^raphy
(1) Alr, delatlon betv/een Dlelectric Constant and Density. A. Occhlallnl. (Accad. Llncei, Attl, 14. pp 613-620, June 3, 1905)
(2) Alr, Dlelectric Constant of at "Tigh Pressiires. K. Tangi, (Ann. d. Hiysik, 25. 3. pp559-574 JUly 5, 1907)
(3) Dlelectric Constante of Oases at ligb Pressur^e. K. Tangi, (An . d. Hiyslk, 26. 1. pp 59-78. ^ ny 12, 1908)
(4) (rases, Dlelectric Constants of for righ f^equency osclllatlons. I. borTir:o.. (Ann. d. Physlk, 34. 5.pp 974-1002. dny 9, 1911)
(5) Air, Dlelectric Constant of at dig"* Presorros. A Occhlallnl. (V. Giinento, 5. de-. 6. ppl5-4d Jan. 1913)
(6) "ir, Dlelectric Constant of at "1:' Pressir^es. (Accad. Llncei, Attl, 22. pp597--0d. ?ay 1913)
(7) Gases, Dlelectric Constants of . d. Plegger. (í nn. d. Physi'#, 5C, 8. pp 753-760. -ept. 1919)
(8) Conductivlty and Dielectr-ie Constant of Dielectrics^it dirb -i-eqi encies. >irsto. (no-^rrl Soe. Proc. 96» .pp 3'3-dd2. "nn. 2, lOlííO)
(9) Dlelectric Constants, Becer. t v orl: on. -Ifbi. (Phys. Teit. 27. pp 226-' :''7. April 15, 1 dJC)
(10) Constant frequency Oscillators. C. .*iller nrd H.''.."ndrer/s. (dev. of 5icientiflc U-istrni-e tri, i, pp 267-27C)
(11) Klectron Tul)es, orecroft, (page 420, 193; )
(12) Klectpic 'oment of 'laseous 'circules of ralogen lyd"ddeo. C «Ta'-!!. {l--ys. Fev. 4 , 4, C:ct. 191^4)
(13) 'nie d l e l e c t r i c Corstnrt of Air nt Dlfferent i-requencies, F.j^.Tplbütt , (Doctorate "bcs ls Cathol lc rni\'e-:^s'ty cf Arc-dcR, 1928)
f l4) m e l c c t ^ l c constant rnd ' o l e c u l - r r t r u o t u r e , C.P.Smyth. {'C:^e Cl er l e a l Catolog C. 1X1)
(15) Dlelectr>ic roe f f i c l en t of ^ a r e s , í ^ r t I I , r ,E . " ' a t son , C.n.^PO , and K.L.^- nasv;--m;< (Toynl ^ >oc. Pvoc. 143, AT50, Feb. 1, lfr.4)