Bhatnagar, G P

Dubey, V S

Gaur, M S

English

IACS Institutional Repository

ELECTROLYTIC EFFECT ON A CURRENT CARRYING CONDUCTORG. P. BHATNAGAR, M. S GAUB, and V. ,S. DUBBYScho ol  oir St u o il s  in  i ’u v b jc s , M a d h a v  (\)l l J''(;k .VjiaiAM U n iv e b s it y , U jj a in  (Received December 22, 1905)ABSTRACT. Effncls  Hiio to  HUporimpoRition oJ‘ oloclrolyiic uuitujiI on a ciuTonl. uniry- jiif^ Gondui't'Or tti*o Htudied b y  direct moauuromonl of Lhe potentia l diffm'i'iifOH uwiiig a Ingh inoiMMoii potoiitiomrttejr. Tlio  positive te rm in a l oi the ideetrolylu current was connected to (1) tfie  positive end o f the heated p la tinum  wire (the elect rolyl ic i urrent adding the heal mg cuiu 'iil/) and (2) tho  negative end o f the heated win- (the e lectiolytic  cuirent o]ip(»Hing the  Inuiting cun O ld ) .  In  both  I he eases the po tentia l ddlmencos across tlic heated platinum  wire  aie calculated fiy assummg pom t to po in t v'^ariation ol tlie euiront along the wu'e. T Ik ' agieo- inm it betw een the  calculated and m easured values is rem arkable for small heid ing cuii'i'iits llo w e v e i a t h igher heating currents the ineasuiod values are found lo he lowei thiin the cal­culated values. This low ering is duo to  the increase in  the leakage current along the wire m  Llie oloetro lyle , as the conductiv ity  of the  e lectrolyte incioases w ith Idle increase ol elei tre lytic  euiTont and also w ith  tho rise in  tom poraturo of the electrelyLe in the v ic in ity  o f tho heated w ire1 N T R O D U O U’ I C) NIliuit traiiKl'er m fluids that aio suhjoctod to an uloutric field has been studied by iSeiiftloben (1931). Similar such problems were then studied by Arajs and Lt^gvold (195S) m different gases and at different jiressures. Mixon, Chon and Beatty (1959) reported tho changes in heat transfer cot^ fficient from a heated siirlatjo duo to electrolytic gas evolution. More recently Bhand d (il (1963, 1963, 1965) have reported the variation in heat transfer cooflicient at different ionic currents sujiorimposod upon cJectrieally heated thin platinum wire transferring heat at a small rate in a weak electrolyte Their contention was that whmi tho so called resistance of the platinum wire decreases, it happens due to the iiicroaso in the heat transfer coefficient, whereas the increase in the resistance was duo to tlio (locreaso in the heat transfer coefficient. Gaur, Bhatnagar and Dubey (1964) using a similar arrangement as that of Bhand ei al have found that there is no adequate evidence to show any marked change in the heat transfer coefficient. This effect is pmoly an electrical phenomenon due to the supenmposition of heat­ing and electrolytic currents on tho platinum wire. The change of resistance attributed by Bhand et al is actually the change of potential difference.The purpose of the present investigation is to measure tho potential differ­ence due to the superimposition of electrolytic current on a ciirient carrying32303304 G. P. Bhatnagar, M. S. Oaur and F . S. DuheypJatirnun wire, directly by a liigli piocisioii jiotcntiometor, and to study tlie effect in greater details.E X  r  E J1 I M E N T A LA HcJieiiiatio diagram of the cquiimieiit used in the present investigation is slioAvn 111 Fig. I A hjKi platinum wire (0 015 (an in diameter and 15 2 cm in longtJi) is dipped hoiizoiitaplly in a Aveak idectrolyte (here tap water) in a large tubat 2S"C The i)latijium avitc' is surrounded by a co-axial cylinder and th(‘, elec­trolytic current is i^roduced by ajijilying a potential difference between the cy- liiuhsr and one end of th(‘ ])latinum wire from a 1^  C Compound Generator G.E.C. F 2A The remotci temperature of tin* bath was kept constant Avnthin 0.5"C.A heuting current is passed through the platinum wire Avhich is kept constant and is measured by a verniei potentiometer by mea.siiTing the potential difference aci'(»ss a standard r(;sisLanc;e of 1 ohm in sewies with the wire The potential differeiuie developiid across the platinum wire is also measured irith the same jiotentiometer.Firstly, the x^‘>teiitial difference across the iilatinum wire is measured at different heating currents and effective riisistance is then found out by dividing the measuriMl iiotential difference with the respoe-tive currents (I). A graph is then plotted beWeen effeiitivc resistance and currchit squared (i^) Fig 2,Secondly, the jiositive end of the jilatinum wire (as shown at A in Fig. 1) is made the xiositive electiode for tlu' electiolytie current and at each value of heating current (T) the xdatimiiii wire is subjected to diffia'ent electrolytic currents ujito 1000 mA. (current densities 1 390 amj)./sq.cm.) and the resultant potential difiereiicc on the iilatinum wire is measured keeping I constant Fig. 3 solid linesarc the plot of measured potential differences versus eloctroljrtic current (a;) for different values of heating currents ranging from 0 to 2 0 amps.Electrolytic Effect on a Current Carrying Conductor 305Fig. 2. P lot o f  Effective raaistance Rg  versus hoating fuiTent squared J2.Thirdly, tlio electrolytic; current was fed from the negative end of the idatinum wire (as shown at B in Fig. 1) still keeping it as jiositive electrode lor the electro­lytic c;urront. TJie resultant iiotontial ditferenccs wore then again measured for the same values of heating and electrolytic currents. Fig 4 solid lines are the plot of the measured potential differences versus electrolytic current for different values of I.T H E O R E T I C A L  C O N S I D E R A T I O N S(1) Wlien the positive end of the heated platinum wire is connected to the I)OHitivc terminal of electrolytic current, it is quite evident tliat the olectrol3dic current var^dng from x to 0 will flow along the wire. Taking any length dl and p as the resistance per imit length of the wire, the potential difference across the element will hewhere i is the electrolytic current in the element dl and is a funcitin of 1. that is i =  0 at Z =  0 (end B of Fig. 1) and i =  x a t l  =  I (end A of Fig.l)Hence the total potential difference across the wire will beS p dl{I-\~i)i i=  S  fiidl=  p l l+ p l^whoro pi — i?eTht> effoi:iivo rosietanoo 11^  at any instant will depend upon the heating power llj^  and therefore, it is necessary that to know the effeetive resistance fhe heating i)OW(ir lij'^ must he known. Considering the current flowing in the wire from {I+x)  to 1, the power will bo \k p d lil^ if  \" \— S pl^dl-\-^ 2plidl~\- S pi^dl— plI -^\-plIx~\-pl —— pl{P~\-l'X-\-X I^2)^  B,{I^-\-Ix-\-x^l3).Tlierefore, for a jjarlieiilar electrolytic current a; at a heating current I  the (effective resistance is foimd out from 7® versus R^  graph for {I'^ ~\-Tx-{-s(^ l3) ciiiTcnt squan^d value and that this value of R  ^ is used to calculate t]ie i)otential differenc(  ^ aciross tho wir(^  Viz. Rg,{T~\-xj2). The points marked cross {X) and curves represented by dotted linos in Fig 3 represent the calculated potential differenc.es at different electrolytic currents.(2) Similarly, vdion tho negative end of the platinum wire is made positive ttaininal for tho electrolytic current, the current flowing in the wire varies from 7 to (7- a?) and hence tho heating power will boS p dl{I-t)^0=  s  p iH i -k  2p iid i+ i pirnS06 O. P. Bhatnagar, M» 8, Oaur and V. 8. Duhey— plP—plIx-irpl Y-  JJ. (7Wa:+a:a/3).The effective roBistance R, is found out from the graph of i f , and P  for {n ~ I x  + x ‘ /3) and this value o f if„ is used for calculating the resultant potential differ-Electrolytic Effect on «  Current Carrying Conductor 307Fig. 3. Plot of calculated and measured potential difforoncos (V ) voraus electrolytic current (x) for electrolytic curront adding the heating current.Siiico here i == x a.t I == 0 (end B *of Fig.Jl) and i =  0 at I ~  I (end A of Fig 1)The resultant potential difference in this case will hokpdl(J-i)l iS  pldl—^  pidl0 Q=  Roil-^12).Tlio pointH markorl by crosH (X ) and curves represented by dotted lines in Fig. 4 roinesont tlie calculated i>otential dilToronccs in this ease.Tablets (J) and (2) illustrate the examples of calculating the potential dif­ferences in the two cases for /  — 2 0 amps. The corresponding measured i)oten_ tial differences arii also shown for the purpose of comparison. i(3) Whenever a current /  is passed in a condutitor (wire) dipped in ami elec- lyte it is very clear that the whole of the cuTrent I will not pass through thA wire, but a portion of it in the form of leakage current will pass througp the308 Q. P. Bhatnagar, M, S. Oaur and F . S. Duhey0 200 400 30 000 800 1000Fif? 4 Plofi o f cnlculatof] and meaanvod po ten tia l differences (V ) versus e lectro lytic  current (a:) fo r e lectrolytic current opposing the  heating  current,olectrolyfce depending upon its conductivity. Tliusif iJislKoafUialTOHistaiKicoi the wire thouR{I~i,i) ■= RJWhen an electrolytic current is passed, the conductivity of tlio clc(;ti olyte mrrcascs and after attaining a maximum value becomes constant T)ue to tliis increase in the conductivity of the ele(5trolyte the value of the leakage cniTont mcireases say by an amount i/p and lionce the not potential dil'lereuce m the two cases willEleetrolytic Effect on a Current Carrying Conductor 309bo R,,( I^—i'p and R,{T—i'fi~I N" T  E R  r  H T  A  T I  O N O E R E S U L T S(1) In figures 3 and 4 looking to the calculated and measured values of tlie ]ioteiitial difforouccs across the platinum wire wo hud that upto 1 0 ampere of heating curi'ent where tlie increase m the leakage current that is I'p is veiy small (which is also evident from the observations of dlt by Gaur, Bhatnagar and Duboy, 1964) tho two values are almost identical. However wluiu the increase of I'p becomes effective, that is above 1 25 amperes of heating current, ive find that the (jahailatccl values of the potential dillbrcnces arc. gicater than tin; inoasurod ones.TABLE TValues of potential differences for electrolytic cuiTents adding the heating current. {I — 2.0 amps.)No.XinA.(7i!+/a;+a;a/3)(Amps) 2Reohms Amps.G'aloulated 1* Jl. VolLrtMoasurofJVT>Volta1. 10 4 020 1.0425 2 005 2.089 2 07642. 20 4 040 1 0427 2 010 2 095 2.07003. r>o 4.100 1 0430 2.025 2 112 2.07384 100 4.203 1.0440 2.050 2 142 2.09685. 200 4.413 1.0460 2.100 2 197 2 15086. 300 4.630 1.0480 2 150 2 253 2.20767. 400 4 850 1.0502 2 200 2 311 2 25808. noo 5.080 1.0530 2.250 2 370 2.31949. 600 6 .320 1 0660 2.300 2.429 2.376410. 800 6 810 1 0590 2 400 2 543 2 497211. 1000 6.333 1.0650 2.600 2 663 2 6114310 O. P. Bhatnagar, M. S. Oaur and F . S. DuheyTABLE IIValues of potential difforcMicos for oloctrolytic currents opposing the heating cun’ent. ( /  =  2.0 amps.)34. fi. G. 7.5.!).JO.raA (Amyjs) 2 oh ms1020fiO100200300400500GOO8003 9803 9003.9003 8033 G133.4303.2633.0832 920 2,6131 04201 04171 04101.04001 03821 .03G.51 03471.03101.0290  1.0260( f —a.’/2) Calciiliitod MeaBiirodAmps. P.JJ. P.D.Voli.s Volts1 9961 .9901 9751.9501.9001.8601 8001 7501 700 1 6002 0782.0732.0562 0281 .9721.9171 8621 8051 750 1 6422 0626 2 0486 ^.0226  i  9938 1^94001 .W o1.83941 79001.7398  1 6392The difference m both the cases should bo equal to i'p * However wo find that this difference R^  i'p in calculated and measured values goes on increasing in the case of Rg{l-\-xl2) values whereas it decreases and even lau'onios zero in the case of R(^T x/2) which requires an explanation The explanation is not far to find. We know that tlie conductivity of an electrolyte increases with the rise in tiaiiperature (Glasstone 1956).^  =  A25[1+A;(«-25)]where A, and A25 are the equivalent conductivities at ^"0 and 25°C and Jc is a cons­tant for an electrolyte Therefore in the case of i2p(7+.'r/2), Fig 3 the temperature of the wire and hence the conductivity of the electrolyte goes on imueasing and therefore, the difference between tjalcjulated and measured values goes on increas­ing with the oloctrolytic current. Whereas, in the case of J2p(/~a:/2), Fig 4 the temperature tif the platinum wire goes on decreasing and hence i'p becomes very small tliereby the calculated and measured values almost coincide.In addition to these wo have one more point of interest to consider and that is tlic electrode heating depending upon the oloctrolytic current densities. Bock and Putnam (1951) showed tliat large tomporatiu’e differences (AT) between anode and the elccti'olyto were observed and therefore, duo to the electrode heating also tliero vull be an increase in the value of Rg and hence the measured values of the potential differences are found slightly higher than the calculated potential differences for the curves for which i'p is small. In other cases where i'p is large this effect is masked,Electrolytic Effect on a Current Carrying Conductor 311C O N C L U S I O N SFrom the above discussion it becomes quite clear that wlioii the oloctroJytii! current is superimposed upon a current carrying conductor, point lo point varia­tion ol tlio cm rent along the wire should bo considcrt>d. Thus when the electro­lytic current is adding the heating current, the potential difference across tlic^  wireR ,  ( / - I  x j2 )and when the electrolytic current is opposing the heating ciineiit, the potential dilfcrence becomesR, {I -x l2 )whore R  ^ is the effective rosistanco of the wne at that timrjWhen the electrolytic current is adding the heating iMirront, the differtuce 111 the cahulatud and measured iiotcntial diffei’encos is due to the increase in the leakage cuneiit, as the conductivity of the clectiolyte increases with the increase*, in the elec-trolytic current as reported earlier by Gaur et al. and rise in temperature of tJie electrolyte in the vicinity of the wire When the electrolytic cuirout is ojjposmg the heating current the conductivity of tlie electrolyte decreases with the decrea,ye in the temjiei'ature of the electrolyte in the vicinity of the iviroThis dilfcrence is certainly not due to the change m the heat transfer coefELcient oi‘ resistance of the wire, as reprtod by Bhand et al.With these results it is therefore concluded that in all cxpermionts of heat transfer where a naked wire liS dipped in a liquid, tin; iiieasurt' of tlie resistance of the wire is erroneous due to the leakage ol current in the liijuiil Also wJien the temperature of the liquid near the wire rises, the molecules ol the liquid become mobile, the conductivity of the liquid is hound to increase, which inc.roasos the leakage current. Hence the measm-e of the resistance will not give the correct temperature of the wire.Therefore, in all such experiments for correct estimation of tlie resistance and hence the tomperatm’e of the wire, a suitable correction will have to be applied lor the fraction of the leakage current passing through the liquid.A C K N O W L E D G E M E N T SWo express our gratitude to Dr. Shiv Mangal Singh ‘Suman’ Principal, Madhav College, U3jain for constant encouragement and to Shri P. S. ICale, Asstt. Professor, Department of Physics, Madhav College for providing the facilities to carry out these investigations. We are also grateful to Dr. V . S. Dubey lleader, Head of School of Studies in Physics, Vikram University Ujjain for his constant guidance and suggestions in the theoretical interpretations of the results.312 G. P. Bhatnagar M, S. Oaur and F* 8, DubeyB E F E K E N C E SAnija. S and Legvold, S. 1958, J. Chtm. Phyiy, 29, 631.Bi'clt T. K and Putnam Gl. 1^ ., 1951, Ind. Eng. Chem. 43, 1123 Bliaud S C , Gauv. M. S. and Goguto. D. V , 1963, Indian. J. Phys 37, 185.Illiand, iS C , Patgaonkar, G. V. and Gogato, D V., 1963, Indian J. Pure, A2);pl. Phy6 , 1, 291.----------------------------- ----------------------------------------- , 1965, Int. J. Heat Maas Trana.,8, 111.Gam M, S-, Bhainagar, G P and Duboy, V. S 1964, Indian J Phya. 38, 509. GlasHtoiio, S 1!)56, Tavt Book of Physical Chemialry II Edn. (Mac Millan ^ Co. Ltd. London) 895Mixon, F ()., Chon, W. Y and Eoatty, K. O. 1959, Chem. Engg. Progr. 55, < Sonltlobeii, H. 1931, Physik Z. 32, 560.

Electrolytic Effect on a Current Carrying Conductor

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Electrolytic Effect on a Current Carrying Conductor

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