Gouy Balance Nonlinear Slope (Magnetic Susceptibility Lab)

1. Feb 1, 2014

djh101

I am currently analyzing my data for the physical chemistry magnetic susceptibility lab. All the data is giving nice, smooth graphs for force vs. current, but I am unable to linearize them.

$F = \frac{1}{2}\chi\mu_{0}AH^{2}$

I have plotted force vs. current and force vs. current squared (current should be proportional to field, so using current shouldn't affect the slope). The former gives an upward moving curve while the latter gives a downward moving curve, so neither is linear. However, fitting a second degree polynomial gives a very good fit to the former (R2 = .997) and a near perfect fit to the latter (R2 = .999). What might be a possible explanation for the nonlinearity?

The only thing I can think of would be an inaccurate current reading, but even doubling the current (making it higher than the current setting, which was already higher than the actual current) doesn't completely kill of the nonlinearity. Any ideas?

http://onlinesciencetools.com/_miscfiles/nicl2.png