Nope. It is nothing about the homework, but a part of my on-going
program. I agree with you on the issue that A1 and B1 act as a new
electrode pair. But the voltage difference between them should be
sinusoidal with a frequency 10KHz and an very low amplitude(since A1-
A2 and B1-B2 are symmetric), how can it trigger a water
eletrolysis...
On Nov 13, 1:09 am, Salmon Egg <Salmon...@[EMAIL PROTECTED]
> wrote:
> On 11/12/07 7:00 PM, in article
> 1194922802.829179.171...@[EMAIL PROTECTED]
"Wener"
>
>
>
>
>
> <lvwe...@[EMAIL PROTECTED]
> wrote:
> > I encountered an strange electrochemical problem in my recent
> > experiments, which really drove me crazy.
>
> > Since I do not know how to attach a image with my post, the following
> > URL will links to the figure of my problem.
> >http://web.mit.edu/lvwener/www/Rig.jpg
>
> > As shown in left part of the attached figure, I am using an cubic
> > acrylic tank of 10cm by 10cm by 10cm, containing a saline solution of
> > conductivity 1mS/cm.
>
> > 1 pair of surface platinum electrodes (A1-A2) is mounted through the
> > wall of the tank, at midpoints of two opposite walls.
>
> > By using a voltage-controlled current source shown by the right part
> > of the attached figure, a 10 kHz sinusoidal signal was converted into
> > a sinusoidal current of fixed peak amplitude 0.25 mA.
>
> > No air bubble was observed.
>
> > Then, another platinum eletrode pair (B1-B2) was added into this
> > system, i.e., I applied sinusoidal current signals through both A1-A2
> > and B1-B2 simultaneously. As shown by left figure, B1-B2 is fixed at
> > midpoints of other two opposite walls.
>
> > Shown by the right figure, the current signal between B1-B2 was
> > generated by the same function generation and similar conversion
> > circuit.
>
> > HOWEVER, now things became totally different, since tons of air
> > bubbles can always be observed at A1 and B1.
>
> > After I read some references on 'water electrolysis', I become even
> > more confused:
> > (1) Since B1-B2 is at the symmetric positions with A1-A2, which means
> > the equivalent resistance between A1-A2 is identical to that between
> > B1-B2, no large voltage difference between A1 and B1 should be
> > expected.
> > (2) Even though there is such a voltage difference, since the
> > frequency is as high as 10KHz, the eletrolysis phenomenon should not
> > be so rapid.
> > (3) If a 10KHz current signal is enough to induce such a terrible
> > electrolysis, Why did not it arise when I had only A1-A2? The
> > frequency is always 10KHz, and the voltage difference between A1-A2
> > should be much larger than between A1-B1.
>
> > Can anybode help me explain this phenomenon, and give me some
> > suggestion about how to avoid the bubble generation during my multi-
> > electrodepair experiment????
>
> > Millions of thanks!!!
>
> > P.S. (1), after a calucation with conductivity value, the equivalent
> > resistance of the saline between A1-A2 (or B1-B2) is approximately
> > given by 6.4 Kohm.
> > P.S. (2), when I measured the potentials at each electrodes, I found
> > DC voltage difference between A1 and A2, between B1 and B2, between
A1-
> > B1. And the DC voltage difference ranges from 0.x Volts to x Volts. I
> > still cannot figure the source of this DC component:
> > (i) the DC offset of my function generator is as low as uV
> > level;
> > (ii) this DC difference was also observed when there was
> > only a single electrode pair A1-A2. Why did not it cause any
> > electrolysis at that time?
> > (iii) I am not sure if there does exist such a DC
> > difference, or it is just becuase the ru****ng air bubbles disturbed my
> > voltage measurement.
>
> I am having difficulty understanding your description. Maybe more
diagrams,
> a table of conditions with results, and better description would help.
>
> Is this a homework assignment? I ordinarily try to avoid helping out
with
> such requests.
>
> Whatever else may be going on, A1 and B1 together will act as one
electrode,
> while A2 and B2 will act like another.
>
> Bill- Hide quoted text -
>
> - Show quoted text -
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