Ghose, Snehamoy

Singh, B N

English

IACS Institutional Repository

ON THE EXPERIMENTAL STUDY OF THE EFFECT OF TRANSVERSE h.f. ELECTRIC FIELD ON THE VISCOSITY OF LIQUIDS*By B. N. SINGHANDSNEHAMOY CHOSE[Received jor pHhliealion, .^epicniber 7, iq,43)I.ABSTRACT, Tlif p.ipcr ronlains Uil' ( k-scriplioii 0 / an appHialn.s dcKij^ued by the present authors to .study the effect of high-frequency tran.sver.se electric field on the rate of flow of liquids throngli narrow channels. The apparatus i.s .suitable for liquids having fairly low conductivity (of the order of 10 mho or lessl and for such liquid.s h.f. field.s of the order of several kilovolts/cin. can be applied. The frequency of the h.f. field may be kept at any .suitable value. The authors have u.scd ticld.s of the order of lo* cycles/.sec. Incidentally th( authors have found that in ca.se of xylene (n mixtiire of oitho-, para- and intta-) no change in the rate of flow i.s recorded for fields up to 5 kilovolts cm and even more. In i;a.se of samples of amyl alcohol and ethyl acetate usid by authors Helds up to 1 kilovolt,'cm. could be applied and for Uiis field no change in their rate of flow was noted.During past few years a large niiinber of experimental investigations have been made to .study the effect of electric field on the viscosity of liquids. Such investigations have been nuide will) electric fields whose diiection is either perpendicular or parallel to that of the flow of liquids. Though the results obtained by various workers appear to be rather conflicting with each other there are a few points on which more or less a general agreement may be observed. In the case of uon-polar liquids there is no appreciable effect of either the longitudi­nal or transverse electric field. The longitudinal electric field does uot appear to produce auy effect eveu ou polar liquids. The main controversy, therefore, centres round the different results obtained when the direction of the applied electric field is perpendicular to that of the flow of liquids. The recent experimental results of Menz (1939), Andrade (1940), and Prasad elal, (1941), however, reveal that even in this last case the effect is either negative or if positive appears to be influenced by the conductivity of the experimental liquids. But according to the results of Andrade conductivity as such is not the deter­mining factor, because liquids like benzene condtict without showing any effect. Andrade further suggests that in case of some polar liquids there is a formation of space charges at the electrodes and hence an abnormal anode and kathode fall. I f  this be the case, the field in the body of the liquid is much less than the* Communicated by the Indian Physical Society.32Experimental Study of Efect of Transverse h.f. ElecMc Field 253F ig. t b254 B. N. Singh and Snehamoy Chose"apparent field " ,  namely the applied difference of potential divided by difference between the two electrodes. In view of these possible disturbances the true viscosity effect should be sought with alternating frequency sufficiently high to prevent space charges at the electrodes and sufficiently low to avoid effects due to relaxation time. In the present paper an apparatus designed by the present authors has been described which is suitable for the experimental study of the effect of h.f, transverse electric field on the rate of flow of liquids having fairly low conductivity.The main body of the apparatus is made of fine steel slab with a central circular platform P (shown in fig. ui) on its upper surface, which is silvered and finely polished, There is a central hole C in the jdalform which is connected: to the glass tube T  through a brass U-tube fitted with a liquid-tight stopper j vS. 'rhrcc small thin pieces of mica DU (thickness of the order of ,003 cm.) \ are kept over the polished platform. The inside of the central hole and that \ of the U-tube is also silvered. A circular brass plate B of thickness 6 mm., polished and silvered at its lower surface, is kept over the strips DD. In order to keep the strips well pre.s.sed, a heavy ring of lead L, is keiit over the plate and made tight from above by three screw's fitted in an upper circular plate N made of ebonite. The upper plate B is also provided with a handle A and terminal T ,. The central circular platform has got a rim R R  about 1 mm. high and an annular space M surrounding it. The inner diameter of the circular platform is 4.3 cm. and that of the upper plate is 3.7 cm. Thus ufheu the latter is placed over the former, between the perimeters of the two there is a fair margin of about 3 mm. When the glass tube T  is filled with a liquid, the latter forces up through the hole C, passes slowly through the "narrow space between the platform and the other plate B, then trickles over the rim of the olatform to the annular space and finally escapes through the opening K, which is also fitted with a liquid-tight stopper K . The steel body of the apparatus is provided with another terminal 1% and rests over a thick circular ebonite plateQ. The latter is supported by three firm rigid legs which are permanently fixed to a wooden base fitted with three levelling screws. The upjrer and lower ebonite plates are rigidly held together with three rods screwed to them. The glass tube T  at its lower end is fitted with a rubber stopper over which a layer of mercury is kept to prevent the liquid from coming into contact with the stopper. The electric field is applied between the two terminals Tj and T2 of the apparatus by connecting it in parallel with the oscillating condenser of a radio-frequency oscillator, the range of oscillations in the present case being 10" cycles per sec. to 10 ' cycles*'per sec. (The connections are shown in fig. 2). The h.f. voltage impressed between the two plates of the apparatus is measured by a Moullin voltmeter. When the experimental liquid is poured into the glass tube (stopper K  being closed), it flows through the U'-tube and the central hole comes slowly through the narrow space between the plate end the platform and finally passes over the rim to the annular space. The level of liquid in the glass tube gradually comes down. The time required for the level of liquid to come from a particular mark say Y  to another say Z may be noted with the help of a travelling telescope and a stop watch. It will be seen from the eacperimentalExperimental Study of Effect of Transverse h.f, Electric Field 255data given in table i , that the time of flow of liquid remains fairly constant^ the maxinunn variations being not more than 3 seconds even wlien the time of flow exceeds 15 minutes. Provided the experimental liquid is pure, throughout the flow over such long periods, the li.f. voltage as incasiuod by Moubin volt­meter remains practically constant. The cajiacity of the condenser formed by the plate B and the platform P ib of the order of a few linndjcds of ft/iV and hence suital)le for introduction into h.f. oscillators of such frequencies which satisfy the condition of being sufficiently high to prevent space charges at the electrodes and sufficiently low to avoid effects due to relaxation time. In view of small separation between the plates, the effective valut: of the electric field acting on the liquid passing through the cliannel may be made considerable without the necessity of applying a field of a high order between the plates. Fig. lb  gives a general view of the apparatus.n  X  P E K I M K N T A h  R K S U Iv T  A N D C O N C Tv IJ S I O NIn table i are given the experimental data for liquids xylene fa mixture of ortho-, para- and nieta-), amyl alcohol and ethyl acetate. Tlie experimental values for the conductivity of the same samples of liquids as used tor flow are also given in the last column.The experimental data given in the above table clearly show that in the present apparatus the time of flow of the given liquid remains con.stant within three or four seconds even if the total time of flow extends ui) to 15 miiiules or more* If the effect of the h.f. electric field is, therefore, to alter the rate of flow of a liquid even to a small extent it can be easily detected in the present arrangement. The only drawback in this design is that liquids not having a fairly low conduc­tivity cannot be used. But this defect will be perhaps inevitable in eveiy design.The fact that in the case of liquids having conductivity of the order of ro^nhofields up to 5 kv./cm. or even more can be obtained, shows that if after icpeated distillations samples of liquids having a conductivity of a much less order Ik. used, a much higher field may be applied and conclusive results obtained.From the results already obtained by the present authors it may lie seen that the effect of the h.f. field on the viscosity of xylene (a mixture of ortho-,para- and meta-) is negative for the fields up to the order mentioned above. Inthis case fields of a much higher value were actually applied but could not be 3-M 55P -V256 B. N. Singh and Snehamoy ChoseT able ILiquidXvlciieAmyl aleuliol litliyl ftcetntrApplied Held vults/em.5UQ030005o« )w300I)1000Frequency in cycles per sec.i.n  X 10"It8,1 Jo'*• t *1M j I2.70 X Ju*‘ri X 1 0 'Time of flow v\ ilhout field6176186196166186173«S386387 38538738835635735535635735S1 080 1681 i 6«3 036 937 93Ssec.'I'lme of flow with field618 sec.619 M620 ,,618 „£>'7619386387 .. 38s :, 3 K 6  . .386 „387356357 -  359 .. 355 ..358 .• 3,S« ..1 6 8 1  , ,1682 „  1681 „936 ,, 938 ..93S ,,Conductivity in (mho)6,7 K JO'*/•3 . 1 6  X  1 0 ' "2.45measured due to the al)sence of n voltmetci of suitable range. P'or the samples of amyl alcohol and ethyl acetate used by the authors h.f. fields only up to i  Kv./cm . could be applied. It may be added that the voltage of the high frequency can be increased also by using a more powerful oscillating circuit.The authors express their thanks to Prof. S. P. Prasad, B .A . (Cantab.) for the inlcre,st he has taken in this work. They are also thankful to Principal Kamta Prasad, B.A- (Cantab.) for his useful suggestions. One of us (S. Chose) is also grateful to the (.Government of Bahar for [)roviding him with a scholarship.I'HVSICS C aiioratorv,SciHNCK COM.rC.K,P atna.R I? F F. R F  N C E SAndrade, IL N. da O,, 1940, Proc. Anr,, 32, 753.Menz, IL , 1939, d. Phy^ik, 34. 740.IVasad, S. P., Singli, H. N. and Singh, IL IX, 1911, ^'toc. Jtui, Congress, 19

On the Experimental Study of the Effect of Transverse h.f. Electric Field on the Viscosity of Liquids

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/1332/1/On%20the%20experimental%20study%20of%20the%20effect_Singh%20B%20N.pdf

On the Experimental Study of the Effect of Transverse h.f. Electric Field on the Viscosity of Liquids

Abstract

Similar works

Full text

Available Versions

IACS Institutional Repository