|My science class has conducted an Electrode and
Electrolyte lab. The lab is to observe trends in
voltage using electrodes and varying
concentrations of electrolytes. First attach a
black or red wire to either a tin, copper, or
steel electrodes. Then you have to put two of
them in two separate holes in a board and then
dip them in hydrochloric acid or a sulfuric acid
which are the electrolytes. |
When we had
finished collecting the data my teacher had a
hypothesis that the more concentrated chemicals
would have a higher voltage. We both wanted to
know the reason on why the chemicals with more
concentration had a less voltage.
|Question Date: 2005-03-09|
This is the kind of experiment in which you need
to make several more kinds of measurement to
determine exactly what is going on. For example,
did you measure the current at a given voltage as
you changed the area of the electrodes?
Alternatively, did you try to move the electrodes
closer together and watch the voltage? Why this is
necessary, is that electrolytes conduct currents
both ways between the electrodes.
path is called battery leakage.
general, the voltages you measure should be a
strong function of the different electrode types,
while the current that the battery delivers is
related to both the separation of the electrodes
(declining as the electrodes are separated) the
area of the electrodes (proportional to the area
of the wetted electrode surface) and the
resistance of the measurement circuit. The
decreasing voltage you measured as the electrolyte
concentration is increased may be caused by the
increased leakage in the battery itself, or by
possible changes to the electrode which only occur
for high concentrations of the electrolyte. If you
have the time, I suggest you design a few
additional experiments based on your ideas of what
is happening to try to find out for yourself what
is going on.
It's a current-thing, from the sound of it. The
more electrolytes there are will make the solution
a better conductor, and that means that at a given
voltage, more current will flow through it than a
less electrolytic solution. There is, however, a
limited amount of charge separation possible, and
the charge separation is what creates the voltage.
So, in putting more strain on your battery (or
whatever power source you are using), the overall
voltage is lessened because the power is increased.
The more concentration of chemicals you have, the
bigger current flowing through the electrodes.
The relationship for current and voltages
V = I x R
V is for voltage, I
is for current and R means the resistance that the
currents finds in its way. If you keep R
constant, when the current increases, the voltage
has to drop, in order to maintain the relationship
among them. And this is always the case: more
current, less voltage, and vise versa, less
current, more voltage. We keep R constant, as it
is. When R is big, the current will not flow as
easy as when R diminishes. When you have short
circuits, the current grows a lot, this means that
R is very low in value, and V drops completely.
The voltage produced in a cell is usually only
dependant on the types of metal and electrolyte,
not the concentration of the electrolyte.
However,if you have a higher concentration
electrolyte, generally the cell can produce more
current, which is a different electrical
measurement from voltage. With some measuring
equipment, it may be hard to separate these two.
One way to think of the difference is that current
tells how much electricity is flowing, and voltage
tells what kind of barrier the electricity can get
over. The more current, the more electricity is
flowing, and the higher the voltage, the higher
the barrier it can overcome.Just as an example,
have you ever touched a doorknob and got a nasty
shock?That shock was several thousand volts, but
had very, very little current so it doesn't hurt
you much at all. On the other hand, a battery can
supply lots of current, but has a small voltage,
so you can't shock yourself with it because your
skin is a barrier.
A practical outcome of
all this can be seen in a car. Those batteries
are only 12V; you can get the same voltage from
eight AA batteries, but the current the car
battery can supply is huge compared to those
little AA batteries. Any ideas why?
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