Salt Bridge & Voltaic Cells Experiment

DrDu

Btw, don't you have access to a digital voltmeter ("multimeter") these tend to have a very high internal resistance. Would be interesting to test if the influence of the number of bridges disappears then.

314Jason

Hi, I tried plotting my actual values on the 1/U_v and 1/n axis:



I'm still not sure I understand your graph explanation. But if I know the gradient, then I can plot a line using the points (1/5, 1/0.92) and get something like this:



So we can use this line to find the theoretical value (U_v) from looking at 1/U_v for each 1/n.

But I'd need to figure out the gradient, which is R_b/(R_v U). I would know U from y-intercept, and R_v from voltmeter (though the one I'd used is very overused, so I couldn't find the R_v anywhere on the box/manual: can we assume this is infinity? or at least a really large value).

Also, how do I figure out R_b?

In the graph above, the red line is actually the theoretical values you gave eariler:

How did you figure this out? What assumptions did you make?

Thank you again for all this! :D

DrDu

Very good, I did that graph, too. The relation does not look too linear, what maybe is to be expected since the salt bridges are certainly not too homogeneous.
I was doing a least squares fit. E.g. in Excel you could chose to put a trend line when clicking on the graph. It can also show you the formula of the linear equation, the constant term is then the value 1/U you want.

314Jason

Sorry, I'm just trying to write an explanation to how I came up with the theoretical value (the red line). So you just look at the trend lines from the values in post #10?

How do I use the stuff we did earlier with Ohm's law to explain this?