Fit a curve by hand, after printing your report.
Units:
Convert all the distances to meters (since you are using Excel, this should be easy even though you recorded them in cm).
Generally speaking, distances must always be expressed in meters, not cm.
Note that if you were using the ln-ln graph merely to find the power in the power law, this would not affect your answer - which is why it didn't matter too much for lab report 1. But this time it does. The values I gave you for alpha assume that meters have been used.
How do I find the slope and the y-intercept?
Crucial question indeed! Since now you are graphing in Excel, you need to read them in the equation that excel gives you for the best fit line. Which means it is really really important you get excel to give you this equation!
BTW: for a graph done in Excel, the graph does not need to take the whole page; that's necessary for graphs done by hand because on those it reduces the error involved in reading the values of the y-intercept, etc...
Confused about how to graph the R vs H graph?
What
you need is only the average, the upper bound point and the lower bound
point for each value of H, which would correspond to the following in the example I used in the template:
for example:
first column
represents H (first value, 20.5, second value, 32.5); second column
represents lower bound, average and upper bound for each of these two
values.
0.2 0.17 (average value of R for H = 20.5)
0.2 0.21 (upper bound value of R, i.e. for upper error bar, for H = 35.9)
0.2 0.15 (lower bound value of R, i.e. for lower error bar, for H = 35.9)
and something similar for H = 0.3 (in this example), and for all the other values of H.
You do not need to graph 18 values of R for each value
of H with 5 (or whatever you have) values of H.
However the averages need to be calculated using the 18 values.
Should all the data appear in the table?
No, what you MUST have in your tables are the values of what
you need in order to graph (H, averages of R, values used to draw the
error bars for R, ln R and ln H...).
If you already have tables in
an electronic format that contain more than that, that is if you
had a laptop with you and typed the values directly into it, then don't
waste time "trimming" the extra data out of these tables, include it since it's there.
But if not, definitely don't waste your time adding all the 18 values
for each R in a table/tables, only give what you must.
